Positive resist compositions and patterning process

ABSTRACT

A positive resist composition comprises (A) a resin component which becomes soluble in an alkaline developer under the action of an acid and (B) an acid generator. The resin (A) is a polymer comprising specific recurring units, represented by formula (1). The acid generator (B) is a specific sulfonium salt compound. When processed by lithography, the composition is improved in resolution and forms a pattern with a minimal LER. 
     
       
         
         
             
             
         
       
     
     Herein R 1  is H or methyl, R 2  is an acid labile group, R 3  is CO 2 R 4  when X is CH 2 , R 3  is H or CO 2 R 4  when X is O, R 4  is a monovalent C 1 -C 20  hydrocarbon group, and m is 1 or 2.

CROSS-REFERENCE TO RELATED APPLICATION

This non-provisional application claims priority under 35 U.S.C. §119(a)on Patent Application No. 2008-008890 filed in Japan on Jan. 18, 2008,the entire contents of which are hereby incorporated by reference.

TECHNICAL FIELD

This invention relates to a positive resist composition for themicropatterning technology which is improved in resolution, line densitydependence, and mask fidelity, and forms a pattern with a minimal lineedge roughness, and a patterning process using the same.

BACKGROUND ART

In the recent drive for higher integration and operating speeds in LSIdevices, it is desired to miniaturize the pattern rule. Great effortshave been devoted for the development of the micropatterning technologyusing deep-ultraviolet (deep-UV) or vacuum-ultraviolet (VUV)lithography. The photolithography using KrF excimer laser (wavelength248 nm) as the light source has already established the main role in thecommercial manufacture of semiconductor devices. The lithography usingArP excimer laser (wavelength 193 nm) is under investigation to enablefurther miniaturization and has reached the stage of prototypemanufacture experiments. However, the ArF excimer laser lithography hasnot matured so that many problems must be overcome before the technologycan be applied to an industrial scale of semiconductor manufacture.

The requisite properties for the resist materials complying with the ArFexcimer laser lithography include transparency at wavelength 193 nm anddry etch resistance. Resist materials comprising as a base resinpoly(meth)acrylic acid derivatives having bulky acid-labile protectivegroups as typified by 2-ethyl-2-adamantyl and 2-methyl-2-adamantylgroups were proposed as having both the properties (JP-A 9-73173 andJP-A 9-90637). Since then, a variety of materials have been proposed.Most of them commonly use resins having a highly transparent backboneand a carboxylic acid moiety protected with a bulky tertiary alkylgroup.

While these prior art resist materials suffer from several problems, themost serious problem is the unevenness of a fine line size generallyknown as “line edge roughness” (LER). There is a strong desire to solvethe problem since such unevenness largely affects the performance ofsemiconductor devices manufactured. If it suffices to provide thepattern with a smooth finish, the object may be attained to some extentby setting the molecular weight of a resin at a relatively low level orby selecting such a photoacid generator that the acid resultingtherefrom is more mobile. These approaches, however, extremelyexacerbate such properties as exposure dose dependency, pattern densitydependency, and mask fidelity, and do not entail a reduction of LERbecause fine fluctuations of the mask are enlarged so that the line sizeitself rather becomes uneven. While a further reduction of the patternrule is invariably required, there is a demand for a resist compositionwhich is essentially improved in LER without the sacrifice of resolutionwhile exerting excellent performance in terms of sensitivity, substrateadhesion and etch resistance.

Studies have also been made on photoacid generators. In prior artchemically amplified resist compositions for lithography using KrFexcimer laser, photoacid generators capable of generating alkane- orarene-sulfonic acid are used. However, the use of these photoacidgenerators in chemically amplified resist compositions for ArFlithography results in an insufficient acid strength to scissor acidlabile groups on the resin, a failure of resolution or a lowsensitivity. Thus these photoacid generators are not suited for thefabrication of microelectronic devices.

For the above reason, photoacid generators capable of generatingperfluoroalkanesulfonic acid having a high acid strength are generallyused in ArF chemically amplified resist compositions.Perfluorooctanesulfonic acid and derivatives thereof (collectivelyreferred to as PFOS) are considered problematic with respect to theirstability (or non-degradability) due to C—F bonds, and biologicalconcentration and accumulation due to hydrophobic and lipophilicnatures. With respect to perfluoroalkanesulfonic acids of 5 or morecarbon atoms and derivatives thereof, the same problems are pointed out.

Facing the PFOS-related problems, manufacturers made efforts to developpartially fluorinated alkane sulfonic acids having a reduced degree offluorine substitution. For instance, JP-A 2004-531749 describes thedevelopment of α,α-difluoroalkanesulfonic acid salts fromα,α-difluoroalkene and a sulfur compound and discloses a resistcomposition comprising a photoacid generator which generates suchsulfonic acid upon irradiation, specificallydi(4-tert-butylphenyl)iodonium1,1-difluoro-2-(1-naphthyl)ethanesulfonate. JP-A 2004-2252 describes thedevelopment of α,α,β,β-tetrafluoroalkanesulfonic acid salts fromα,α,β,β-tetrafluoro-α-iodoalkane and sulfur compound and discloses aphotoacid generator capable of generating such a sulfonic acid and aresist composition comprising the same. JP-A 2002-214774 disclosesphotoacid generators having difluorosulfoacetic acid alkyl esters (e.g.,1-(alkoxycarbonyl)-1,1-difluoromethanesulfonate) and difluorosulfoaceticacid amides (e.g., 1-carbamoyl-1,1-difluoromethanesulfonate) althoughtheir synthesis method is lacking. Furthermore, JP-A 2004-4561 disclosestriphenylsulfonium(adamantan-1-ylmethyl)oxycarbonyldifluoromethanesulfonate although itssynthesis method is lacking; JP-A 2006-306856 disclosestriphenylsulfonium alkyloxycarbonyldifluoromethanesulfonates having alactone structure and analogs; and JP-A 2007-145797 disclosestriphenylsulfonium 2-acyloxy-1,1,3,3,3-hexafluoropropanesulfonate andanalogs.

As far as the inventors empirically confirmed, undesirably thesecompounds suffer from problems including difficult compound design dueto limited starting reactants (JP-A 2004-531749, JP-A 2004-2252), lowsolubility (JP-A 2002-214774, JP-A 2004-4561, JP-A 2006-306856), andincreased hydrophobicity due to many fluorine atoms (JP-A 2007-145797).

With respect to the immersion lithography, there remain some otherproblems. Minute water droplets are left on the resist and wafer afterthe immersion exposure, which can often cause damages and defects to theresist pattern profile. The resist pattern after development cancollapse or deform into a T-top profile. There exists a need for apatterning process which can form a satisfactory resist pattern afterdevelopment according to the immersion lithography.

DISCLOSURE OF THE INVENTION

An object of the invention is to provide a positive resist compositionwhich accomplishes both an improvement in resolution and a reduction ofLER when processed by the photolithography using high-energy radiationsuch as ArP excimer laser light as a light source, and a patterningprocess using the same.

The inventor has found that a positive resist composition comprising apolymer comprising specific recurring units as a base resin and asulfonium salt compound having a specific structure as an acid generatorpossesses an excellent resolution performance and a reduction of LER,and is thus quite effective for precise micropatterning.

In one aspect, the invention provides a positive resist compositioncomprising (A) a resin component which becomes soluble in an alkalinedeveloper under the action of an acid and (B) a compound capable ofgenerating an acid in response to actinic light or radiation. The resincomponent (A) is a polymer comprising recurring units (a), (b), and (c)represented by the general formula (1):

wherein R¹ is each independently hydrogen or methyl, R² is an acidlabile group, X is O or CH₂, R³ is CO₂R⁴ when X is CH₂, R³ is hydrogenor CO₂R⁴ when X is O, R⁴ is a straight, branched or cyclic, monovalenthydrocarbon group of 1 to 20 carbon atoms which may contain aheteroatom, and m is 1 or 2. The compound (B) is a sulfonium saltcompound having the general formula (2):

wherein R⁵, R⁶ and R⁷ are each independently hydrogen or a straight,branched or cyclic, monovalent hydrocarbon group of 1 to 20 carbon atomswhich may contain a heteroatom, and R⁸ is a straight, branched orcyclic, monovalent hydrocarbon group of 4 to 30 carbon atoms which maycontain a heteroatom.

In a preferred embodiment, the polymer as resin component (A) furthercomprises recurring units (d) of the following formula:

wherein R¹ is each independently hydrogen or methyl, and n is 1 or 2.

In a preferred embodiment, the acid labile group represented by R² inresin component (A) is one or multiple groups selected from thefollowing formulae (a-1) to (a-8):

wherein the broken line denotes a valence bond, R⁹, R¹⁰, R¹¹, and R¹²are each independently a straight or branched alkyl of 1 to 4 carbonatoms, R¹³ is a straight or branched alkyl of 1 to 4 carbon atoms,cyclopentyl or cyclohexyl, “o” is 1 or 2, and p is 1 or 2.

In a preferred embodiment, the composition may further comprise atertiary amine as an acid diffusion regulator and/or a surfactant whichis insoluble in water and soluble in the alkaline developer.

In another aspect, the invention provides

a process for forming a pattern, comprising the steps of applying thepositive resist composition defined above onto a substrate to form aresist coating, heat treating, exposing the resist coating tohigh-energy radiation through a photomask, optionally heat treating, anddeveloping the exposed coating with a developer;

a process for forming a pattern, comprising the steps of applying thepositive resist composition defined above onto a substrate to form aresist coating, heat treating, applying on the resist coating aprotective coating which is insoluble in water and soluble in analkaline developer, exposing the resist coating to high-energy radiationthrough a photomask, with water interposed between the substrate and aprojection lens, optionally heat treating, and developing the exposedcoating with a developer; or

a process for forming a pattern, comprising the steps of applying thepositive resist composition defined above onto a substrate to form aresist coating, heat treating, imagewise writing on the resist coatingwith an electron beam, optionally heat treating, and developing thecoating with a developer.

In a still further aspect, the invention provides a process for forminga pattern, comprising the steps of applying the positive resistcomposition defined above onto a substrate to form a resist coating,heat treating, exposing the resist coating to high-energy radiationthrough a photomask, heat treating, and developing the coating with adeveloper. The process further comprises the step of applying aprotective coating on the resist coating. The exposing step is effectedby the immersion lithography wherein a liquid having a refractive indexof at least 1.0 intervenes between the protective coating and aprojection lens.

BENEFITS OF THE INVENTION

When processed by the micropatterning process, especially ArFlithography, the positive resist composition of the invention exhibits asignificantly high resolution and forms a pattern with a minimized LER.The composition is thus quite effective for precise micropatterning.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing the ¹H-NMR (DMSO-d₆) spectrum of PAG-1 inExample.

FIG. 2 is a diagram showing the ¹⁹F-NMR (DMSO-d₆) spectrum of PAG-1.

FIG. 3 is a diagram showing the ¹H-NMR (DMSO-d₆) spectrum of PAG-2 inExample.

FIG. 4 is a diagram showing the ¹⁹F-NMR (DMSO-d₆) spectrum of PAG-2.

FIG. 5 is a diagram showing the ¹H-NMR (DMSO-d₆) spectrum of PAG-3 inExample.

FIG. 6 is a diagram showing the ¹⁹F-NMR (DMSO-d₆) spectrum of PAG-3.

FIG. 7 is a diagram showing the ¹H-NMR (DMSO-d₆) spectrum of PAG-4 inExample.

FIG. 8 is a diagram showing the ¹⁹F-NMR (DMSO-d₆) spectrum of PAG-4.

FIG. 9 is a diagram showing the ¹H-NMR (DMSO-d₆) spectrum of PAG-5 inExample.

FIG. 10 is a diagram showing the ¹⁹F-NMR (DMSO-d₆) spectrum of PAG-5.

PREFERRED EMBODIMENTS OF THE INVENTION

Below the resist composition of the invention is described in detail.The singular forms “a,” “an” and “the” include plural referents unlessthe context clearly dictates otherwise.

The notation (Cn-Cm) means a group containing from n to m carbon atomsper group.

It is understood that for some structures represented by chemicalformulae, there can exist enantiomers and diastereomers because of thepresence of asymmetric carbon atoms. In such a case, a single formulacollectively represents all such isomers. The isomers may be used aloneor in admixture.

The resist composition of the invention comprises (A) a resin componentwhich becomes soluble in an alkaline developer under the action of anacid, and (B) a compound capable of generating an acid in response toactinic light or radiation, wherein resin component (A) is a polymercomprising recurring units (a), (b) and (c) represented by the generalformula (1) and compound (B) is a sulfonium salt compound having thegeneral formula (2).

Herein R¹ is each independently hydrogen or methyl, R² is an acid labilegroup, and X is O or CH₂. R³ is CO₂R⁴ when X is CH₂, and R³ is hydrogenor CO₂R⁴ when X is O, wherein R⁴ is a straight, branched or cyclic,monovalent hydrocarbon group of 1 to 20 carbon atoms, preferably 1 to 10carbon atoms, which may contain a heteroatom, such as fluorine. Thesubscript m is equal to 1 or 2.

Preferably, the acid labile group represented by R² in resin component(A) is one or multiple groups selected from the following formulae (a-1)through (a-8).

Herein the broken line denotes a valence bond. R⁹, R¹⁰, R¹¹, and R¹² areeach independently a straight or branched C₁-C₄ alkyl group, such asmethyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl or tert-butyl. R¹³is a straight or branched C₁-C₄ alkyl group, cyclopentyl or cyclohexyl,such as methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl,tert-butyl, cyclopentyl or cyclohexyl. The subscript “o” is equal to 1or 2, and p is equal to 1 or 2.

Illustrative, non-limiting examples of the acid labile group representedby R² are given below.

Illustrative, non-limiting examples of the recurring units (b) in resincomponent (A) are given below, while such units of one type or more thanone type may be used.

Note that R¹ is as defined above.

Illustrative, non-limiting examples of the recurring units (c) in resincomponent (A) are given below, while such units of one type or more thanone type may be used.

Note that R¹ is as defined above.

While the polymer as resin component (A) should comprise recurring units(a), (b) and (c) as essential units, the polymer may further compriseadditional units (d), including carboxylate-terminated recurring units,lactone-containing recurring units, and fluorinated alcohol-containingrecurring units. The preferred additional recurring units (d) arelactone units of the following formula.

Note that R¹ is as defined above, and n is 1 or 2.

Illustrative, non-limiting examples of the additional recurring units(d) are given below.

Note that R¹ is as defined above.

The proportion of recurring units (a), (b) and (c) and optionalrecurring units (d) relative to the entire recurring units within thepolymer as resin component (A) is desirably in the following range:

a/[a+b+c+d]=0.1 to 0.5,

b/[a+b+c+d]=0.05 to 0.4,

c/[a+b+c+d]=0.1 to 0.5. and

d/[a+b+c+d]=0 to 0.3, especially 0.05 to 0.3,

provided that a+b+c+d =1. That is, in a polymer comprising recurringunits (a) to (d), the total of these recurring units (a) to (d) is 100mol % relative to the total of entire recurring units.

The compound (B) is a sulfonium salt compound having the general formula(2).

Herein R⁵, R⁶ and R⁷ are each independently hydrogen or a straight,branched or cyclic, monovalent hydrocarbon group of 1 to 20 carbon atomswhich may contain a heteroatom(s). Exemplary hydrocarbon groups includemethyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, tert-butyl,tert-amyl, n-pentyl, n-hexyl, cyclopentyl, cyclohexyl, ethylcyclopentyl,butylcyclopentyl, ethylcyclohexyl, butylcyclohexyl, adamantyl,ethyladamantyl, and butyladamantyl, and modified forms of the foregoingin which any carbon-carbon bond is separated by a hetero atomic groupsuch as —O—, —S—, —SO—, —SO₂—, —NH—, —C(═O)—, —C(═O)O— or —C(═O)NH— orin which any hydrogen atom is substituted by a functional group such as—OH, —NH₂, —CHO, or —CO₂H.

R⁸ is a straight, branched or cyclic, monovalent hydrocarbon group of 4to 30 carbon atoms which may contain a heteroatom(s), examples of whichare given below, but not limited thereto.

Note that the broken line denotes a valence bond.

The compound (B) capable of generating an acid in response to actiniclight or radiation may be synthesized by the following process, forexample.

One exemplary compound may be synthesized by reacting2-bromo-2,2-difluoroethanol with a carboxylic chloride to form2-bromo-2,2-difluoroethylalkane carboxylate or2-bromo-2,2-difluoroethylarene carboxylate, converting the bromo groupinto sodium sulfinate using a sulfur compound such as sodium dithionite,and converting sulfinic acid into sulfonic acid using an oxidizing agentsuch as hydrogen peroxide. The steps of esterification, conversion fromalkane halide to sodium sulfinate, and conversion to sulfonic acid arewell known, while the formulations used in the latter two steps aredescribed in JP-A 2004-2252. The outline of the process is illustratedbelow.

Note that R⁸ is as defined above.

Subsequent ion exchange reaction between the resulting sodium sulfonateand a sulfonium salt compound yields the desired compound (B) capable ofgenerating an acid in response to actinic light or radiation, asrepresented by formula (2). With respect to ion exchange reaction,reference is made to JP-A 2007-145797.

Further, the acyl group R⁸CO— introduced as above is subjected to esterhydrolysis or solvolysis and then acylated again whereby a substituentgroup different from the initially introduced acyl group can beintroduced. The outline of the process is illustrated below.

Note that R⁵ to R⁸ are as defined above, and X is a halogen atom.

This formulation makes it possible to introduce a substituent groupwhich is unstable under the conditions of the previous anion synthesisprocess (conversion of a bromo group into sodium sulfinate using asulfur compound such as sodium dithionite and subsequent conversion ofsulfinic acid into sulfonic acid using an oxidizing agent such ashydrogen peroxide).

In formula (1), the recurring unit (c) has a high affinity to alkalinedeveloper and is moderately dissolved in the developer, so thatformation of a swollen layer is inhibited, reducing line edge roughness(LER). This unit, however, has a low ability of inhibiting aciddiffusion, allowing the acid to diffuse during heat treatment afterexposure, often referred to as post-exposure baking (PEB). Thisexacerbates such properties as exposure dose dependency, pattern densitydependency, and mask fidelity. Making efforts to solve this problem, theinventors have found that a 1,1-difluoroethanesulfonic acid derivativeis a substantially low diffusible acid, that a sulfonium salt compoundof the above general formula (2) capable of generating that acid is aneffective acid generator, and that a combination of this sulfonium saltcompound with a polymer having general formula (1) gives a resistcomposition which is improved in both resolution and LER.

More particularly, exemplary preferred configurations of polymers asresin component (A) are given below, but not limited thereto.

The polymer as resin component (A) should preferably have a weightaverage molecular weight (Mw) of 1,000 to 50,000, and more preferably2,000 to 30,000, as measured by gel permeation chromatography (GPC)versus polystyrene standards.

The polymer as resin component (A) may be obtained throughcopolymerization of (meth)acrylic ester derivative monomerscorresponding to the respective recurring units by any well-knowntechnique such as radical polymerization. It is noted that the polymersused in Examples to be described later were synthesized from preselected(meth)acrylic ester derivative monomers by a standard radicalpolymerization technique.

Preferred examples of sulfonium salt compounds as the compound capableof generating an acid in response to actinic light or radiation (B) aregiven below, but not limited thereto.

Other Resin Component

In addition to resin component (A) or polymer having formula (1), theresist composition of the invention may further comprise another resincomponent.

The resin component other than resin component (A) that can be added tothe resist composition includes, but is not limited to, polymerscomprising units of the following formula (R1) and/or (R2) and having aweight average molecular weight of 1,000 to 100,000, especially 3,000 to30,000, as measured by GPC versus polystyrene standards.

Herein, R⁰⁰¹ is hydrogen, methyl or CH₂CO₂R⁰⁰³. R⁰⁰² is hydrogen, methylor CO₂R⁰⁰³. R⁰⁰³ is a straight, branched or cyclic C₁-C₁₅ alkyl group,examples of which include methyl, ethyl, propyl, isopropyl, n-butyl,sec-butyl, tert-butyl, tert-amyl, n-pentyl, n-hexyl, cyclopentyl,cyclohexyl, ethylcyclopentyl, butylcyclopentyl, ethylcyclohexyl,butylcyclohexyl, adamantyl, ethyladamantyl, and butyladamantyl.

R⁰⁰⁴ is hydrogen or a monovalent hydrocarbon group of 1 to 15 carbonatoms having at least one group selected from among fluorinatedsubstituent groups, carboxyl groups and hydroxyl groups. Examplesinclude hydrogen, carboxyethyl, carboxybutyl, carboxycyclopentyl,carboxycyclohexyl, carboxynorbornyl, carboxyadamantyl, hydroxyethyl,hydroxybutyl, hydroxycyclopentyl, hydroxycyclohexyl, hydroxynorbornyl,hydroxyadamantyl,[2,2,2-trifluoro-1-hydroxy-1-(trifluoromethyl)ethyl]cyclohexyl, andbis[2,2,2-trifluoro-1-hydroxy-1-(trifluoromethyl)ethyl]cyclohexyl.

At least one of R⁰⁰⁵ to R⁰⁰⁸ represents a carboxyl group or a monovalenthydrocarbon group of 1 to 15 carbon atoms having at least one groupselected from among fluorinated substituent groups, carboxyl groups andhydroxyl groups while the remaining R's independently represent hydrogenor straight, branched or cyclic C₁-C₁₅ alkyl groups. Examples ofsuitable monovalent C₁-C₁₅ hydrocarbon groups having at least one groupselected from among fluorinated substituent groups, carboxyl groups andhydroxyl groups include carboxymethyl, carboxyethyl, carboxybutyl,hydroxymethyl, hydroxyethyl, hydroxybutyl, 2-carboxyethoxycarbonyl,4-carboxybutoxycarbonyl, 2-hydroxyethoxycarbonyl,4-hydroxybutoxycarbonyl, carboxycyclopentyloxycarbonyl,carboxycyclohexyloxycarbonyl, carboxynorbornyloxycarbonyl,carboxyadamantyloxycarbonyl, hydroxycyclopentyloxycarbonyl,hydroxycyclohexyloxycarbonyl, hydroxynorbornyloxycarbonyl,hydroxyadamantyloxycarbonyl,[2,2,2-trifluoro-1-hydroxy-1-(trifluoromethyl)ethyl]cyclohexyloxycarbonyl,andbis[2,2,2-trifluoro-1-hydroxy-1-(trifluoromethyl)ethyl]cyclohexyloxycarbonyl.Suitable straight, branched or cyclic C₁-C₁₅ alkyl groups are asexemplified for R⁰⁰³.

Two of R⁰⁰⁵ to R⁰⁰⁸ (for example, a pair of R⁰⁰⁵ and R⁰⁰⁶, R⁰⁰⁶ andR⁰⁰⁷, or R⁰⁰⁷ and R⁰⁰⁸) may bond together to form a ring with the carbonatom(s) to which they are attached, and in that event, at least one ofring-forming R⁰⁰⁵ to R⁰⁰⁸ is a divalent hydrocarbon group of 1 to 15carbon atoms having at least one group selected from fluorinatedsubstituent groups, carboxyl groups and hydroxyl groups, while theremaining R's are independently single bonds, hydrogen atoms orstraight, branched or cyclic C₁-C₁₅ alkyl groups. Suitable divalentC₁-C₁₅ hydrocarbon groups having at least one group selected fromfluorinated substituent groups, carboxyl groups and hydroxyl groupsinclude those exemplified above as the monovalent hydrocarbon groupshaving at least one group selected from fluorinated substituent groups,carboxyl groups and hydroxyl groups, with one hydrogen atom eliminatedtherefrom. Suitable straight, branched or cyclic C₁-C₁₅ alkyl groups areas exemplified for R⁰⁰³.

R⁰⁰⁹ is a monovalent hydrocarbon group of 3 to 15 carbon atomscontaining a —CO₂— partial structure. Examples include 2-oxooxolan-3-yl,4,4-dimethyl-2-oxooxolan-3-yl, 4-methyl-2-oxooxan-4-yl,2-oxo-1,3-dioxolan-4-ylmethyl, and 5-methyl-2-oxooxolan-5-yl.

At least one of R⁰¹⁰ to R⁰¹³ is a monovalent hydrocarbon group of 2 to15 carbon atoms containing a —CO₂— partial structure, while theremaining R's are independently hydrogen atoms or straight, branched orcyclic C₁-C₁₅ alkyl groups. Illustrative examples of suitable monovalentC₂-C₁₅ hydrocarbon groups containing a —CO₂— partial structure include2-oxooxolan-3-yloxycarbonyl, 4,4-dimethyl-2-oxooxolan-3-yloxycarbonyl,4-methyl-2-oxooxan-4-yloxycarbonyl,2-oxo-1,3-dioxolan-4-ylmethyloxycarbonyl, and5-methyl-2-oxooxolan-5-yloxycarbonyl. Suitable straight, branched orcyclic C₁-C₁₅ alkyl groups are as exemplified for R⁰⁰³.

Two of R⁰¹⁰ to R⁰¹³ (for example, a pair of R⁰¹⁰ and R⁰¹¹, R⁰¹¹ andR⁰¹², or R⁰¹² and R⁰¹³) may bond together to form a ring with the carbonatom(s) to which they are attached, and in that event, at least one ofring-forming R⁰¹⁰ to R⁰¹³ is a divalent hydrocarbon group of 1 to 15carbon atoms containing a —CO₂— partial structure, while the remainingR's are independently single bonds, hydrogen atoms or straight, branchedor cyclic C₁-C₁₅ alkyl groups. Illustrative examples of suitabledivalent C₁-C₁₅ hydrocarbon groups containing a —CO₂— partial structureinclude 1-oxo-2-oxapropane-1,3-diyl, 1,3-dioxo-2-oxapropane-1,3-diyl,1-oxo-2-oxabutane-1,4-diyl, and 1,3-dioxo-2-oxabutane-1,4-diyl, as wellas those exemplified as the monovalent hydrocarbon groups containing a—CO₂— partial structure, with one hydrogen atom eliminated therefrom.Suitable straight, branched or cyclic C₁-C₁₅ alkyl groups are asexemplified for R⁰⁰³.

R⁰¹⁴ is a polycyclic hydrocarbon group having 7 to 15 carbon atoms or analkyl group containing such a polycyclic hydrocarbon group. Examplesinclude norbornyl, bicyclo[3.3.]nonyl, tricyclo[5.2.1.0^(2,6)]decyl,adamantyl, norbornylmethyl, and adamantylmethyl as well as alkyl- orcycloalkyl-substituted forms of the foregoing. R⁰¹⁵ is an acid labilegroup, which will be described later in detail. R⁰¹⁶ is hydrogen ormethyl. R⁰¹⁷ is a straight, branched or cyclic C₁-C₈ alkyl group,examples of which include methyl, ethyl, propyl, isopropyl, n-butyl,sec-butyl, tert-butyl, tert-amyl, n-pentyl, n-hexyl, cyclopentyl andcyclohexyl. X is CH₂ or an oxygen atom. Letter k is 0 or 1.

The acid labile group represented by R⁰¹⁵ may be selected from a varietyof such groups to be deprotected with the acid generated from thephotoacid generator. It may be any of well-known acid labile groupscommonly used in prior art resist compositions, especially chemicallyamplified resist compositions. Examples of the acid labile group aregroups of the following general formulae (L1) to (L4), tertiary alkylgroups of 4 to 20 carbon atoms, preferably 4 to 15 carbon atoms,trialkylsilyl groups in which each alkyl moiety has 1 to 6 carbon atoms,and oxoalkyl groups of 4 to 20 carbon atoms.

Herein, the broken line denotes a valence bond. In formula (L1), R^(L01)and R^(L02) are hydrogen or straight, branched or cyclic alkyl groups of1 to 18 carbon atoms, preferably 1 to 10 carbon atoms. Exemplary alkylgroups include methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl,tert-butyl, cyclopentyl, cyclohexyl, 2-ethylhexyl, n-octyl, andadamantyl. R^(L03) is a monovalent hydrocarbon group of 1 to 18 carbonatoms, preferably 1 to 10 carbon atoms, which may contain a heteroatomsuch as oxygen, examples of which include unsubstituted straight,branched or cyclic alkyl groups and substituted forms of such alkylgroups in which some hydrogen atoms are replaced by hydroxyl, alkoxy,oxo, amino, alkylamino or the like. Illustrative examples of thestraight, branched or cyclic alkyl groups are as exemplified above forR^(L01) and R^(L02), and examples of the substituted alkyl groups are asshown below.

A pair of R^(L01) and R^(L02), R^(L01) and R^(L03), or R^(L02) andR^(L03) may together form a ring with carbon and oxygen atoms to whichthey are attached. Each of R^(L01), R^(L02) and R^(L03) is a straight orbranched alkylene group of 1 to 18 carbon atoms, preferably 1 to 10carbon atoms when they form a ring.

In formula (L2), R^(L04) is a tertiary alkyl group of 4 to 20 carbonatoms, preferably 4 to 15 carbon atoms, a trialkylsilyl group in whicheach alkyl moiety has 1 to 6 carbon atoms, an oxoalkyl group of 4 to 20carbon atoms, or a group of formula (L1). Exemplary tertiary alkylgroups are tert-butyl, tert-amyl, 1,1-diethylpropyl,2-cyclopentylpropan-2-yl, 2-cyclohexylpropan-2-yl,2-(bicyclo[2.2.1]heptan-2-yl)propan-2-yl, 2-(adamantan-1-yl)propan-2-yl,2-(tricyclo[5.2.1.0^(2,6)]decan-8-yl)propan-2-yl,2-(tetracyclo[6.2.1.1^(3,6).0^(2,7)]dodecan-4-yl)propan-2-yl,1-ethylcyclopentyl, 1-butylcyclopentyl, 1-ethyloyclohexyl,1-butylcyclohexyl, 1-ethyl-2-cyclopentenyl, 1-ethyl-2-cyclohexenyl,2-methyl-2-adamantyl, 2-ethyl-2-adamantyl,8-methyl-8-tricyclo[5.2.1.0^(2,6)]decyl,8-ethyl-8-tricyclo[5.2.1.0^(2,6)]decyl,4-methyl-4-tetracyclo[6.2.1.1^(3,6).0^(2,7)]dodecyl,4-ethyl-4-tetracyclo[6.2.1.1^(3,6).0^(2,7)]dodecyl, and the like.Exemplary trialkylsilyl groups are trimethylsilyl, triethylsilyl, anddimethyl-tert-butylsilyl. Exemplary oxoalkyl groups are 3-oxocyclohexyl,4-methyl-2-oxooxan-4-yl, and 5-methyl-2-oxooxolan-5-yl. Letter y is aninteger of 0 to 6.

In formula (L3), R^(L05) is an optionally substituted, straight,branched or cyclic C₁-C₁₀ alkyl group or an optionally substitutedC₆-C₂₀ aryl group. Examples of the optionally substituted alkyl groupsinclude straight, branched or cyclic alkyl groups such as methyl, ethyl,propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, tert-amyl, n-pentyl,n-hexyl, cyclopentyl, cyclohexyl, and bicyclo[2.2.1]heptyl, andsubstituted forms of such groups in which some hydrogen atoms arereplaced by hydroxyl, alkoxy, carboxy, alkoxycarbonyl, oxo, amino,alkylamino, cyano, mercapto, alkylthio, sulfo or other groups or inwhich some methylene groups are replaced by oxygen or sulfur atoms.Examples of optionally substituted aryl groups include phenyl,methylphenyl, naphthyl, anthryl, phenanthryl, and pyrenyl. Letter m isequal to 0 or 1, n is equal to 0, 1, 2 or 3, and 2m+n is equal to 2 or3.

In formula (L4), R^(L06) is an optionally substituted, straight,branched or cyclic C₁-C₁₀ alkyl group or an optionally substitutedC₆-C₂₀ aryl group. Examples of these groups are the same as exemplifiedfor R^(L05). R^(L07) to R^(L16) independently represent hydrogen ormonovalent hydrocarbon groups of 1 to 15 carbon atoms. Exemplaryhydrocarbon groups are straight, branched or cyclic alkyl groups such asmethyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, tert-butyl,tert-amyl, n-pentyl, n-hexyl, n-octyl, n-nonyl, n-decyl, cyclopentyl,cyclohexyl, cyclopentylmethyl, cyclopentylethyl, cyclopentylbutyl,cyclohexylmethyl, cyclohexylethyl and cyclohexylbutyl, and substitutedforms of these groups in which some hydrogen atoms are replaced byhydroxyl, alkoxy, carboxy, alkoxycarbonyl, oxo, amino, alkylamino,cyano, mercapto, alkylthio, sulfo or other groups. Alternatively, two ofR^(L07) to R^(L16) may bond together to form a ring with the carbonatom(s) to which they are attached (for example, a pair of R^(L07) andR^(L08), R^(L07) and R^(L09), R^(L08) and R^(L10), R^(L09) and R^(L10),R^(L11) and R^(L12), R^(L13) and R^(L14), or a similar pair form aring). Each of R^(L07) to R^(L16) represents a divalent C₁-C₁₅hydrocarbon group when they form a ring, examples of which are thoseexemplified above for the monovalent hydrocarbon groups, with onehydrogen atom being eliminated. Two of R^(L07) to R^(L16) which areattached to vicinal carbon atoms may bond together directly to form adouble bond (for example, a pair of R^(L07) and R^(L09), R^(L09) andR^(L15), R^(L13) and R^(L15), or a similar pair).

Of the acid labile groups of formula (L1), the straight and branchedones are exemplified by the following groups.

Of the acid labile groups of formula (L1), the cyclic ones are, forexample, tetrahydrofuran-2-yl, 2-methyltetrahydrofuran-2-yl,tetrahydropyran-2-yl, and 2-methyltetrahydropyran-2-yl.

Examples of the acid labile groups of formula (L2) includetert-butoxycarbonyl, tert-butoxycarbonylmethyl, tert-amyloxycarbonyl,tert-amyloxycarbonylmethyl, 1,1-diethylpropyloxycarbonyl,1,1-diethylpropyloxycarbonylmethyl, 1-ethylcyclopentyloxycarbonyl,1-ethylcyclopentyloxycarbonylmethyl, 1-ethyl-2-cyclopentenyloxycarbonyl,1-ethyl-2-cyclopentenyloxycarbonylmethyl, 1-ethoxyethoxycarbonylmethyl,2-tetrahydropyranyloxycarbonylmethyl, and2-tetrahydrofuranyloxycarbonylmethyl groups.

Examples of the acid labile groups of formula (L3) include1-methylcyclopentyl, 1-ethylcyclopentyl, 1-n-propylcyclopentyl,1-isopropylcyclopentyl, 1-n-butylcyclopentyl, 1-sec-butylcyclopentyl,1-cyclohexylcyclopentyl, 1-(4-methoxybutyl)cyclopentyl,1-(bicyclo[2.2.1]heptan-2-yl)cyclopentyl,1-(7-oxabicyclo[2.2.1]heptan-2-yl)cyclopentyl, 1-methylcyclohexyl,1-ethylcyclohexyl, 1-methyl-2-cyclopentenyl, 1-ethyl-2-cyclopentenyl,1-methyl-2-cyclohexenyl, and 1-ethyl-2-cyclohexenyl groups.

Of the acid labile groups of formula (L4), those groups of the followingformulae (L4-1) to (L4-4) are preferred.

In formulas (L4-1) to (L4-4), the broken line denotes a bonding site anddirection. R^(L41) is each independently a monovalent hydrocarbon group,typically a straight, branched or cyclic C₁-C₁₀ alkyl group, such asmethyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, tert-butyl,tert-amyl, n-pentyl, n-hexyl, cyclopentyl and cyclohexyl.

For formulas (L4-1) to (L4-4), there can exist enantiomers anddiastereomers. Each of formulae (L4-1) to (L4-4) collectively representsall such stereoisomers. Such stereoisomers may be used alone or inadmixture.

For example, the general formula (L4-3) represents one or a mixture oftwo selected from groups having the following general formulas (L4-3-1)and (L4-3-2).

Similarly, the general formula (L4-4) represents one or a mixture of twoor more selected from groups having the following general formulas(L4-4-1) to (L4-4-4).

Each of formulas (L4-1) to (L4-4), (L4-3-1) and (L4-3-2), and (L4-4-1)to (L4-4-4) collectively represents an enantiomer thereof and a mixtureof enantiomers.

It is noted that in the above formulas (L4-1) to (L4-4), (L4-3-1) and(L4-3-2), and (L4-4-1) to (L4-4-4), the bond direction is on the exoside relative to the bicyclo[2.2.1]heptane ring, which ensures highreactivity for acid catalyzed elimination reaction (see JP-A2000-336121). In preparing these monomers having a tertiary exo-alkylgroup of bicyclo[2.2.1]heptane structure as a substituent group, theremay be contained monomers substituted with an endo-alkyl group asrepresented by the following formulas (L4-1-endo) to (L4-4-endo). Forgood reactivity, an exo proportion of at least 50 mol % is preferred,with an exo proportion of at least 80 mol % being more preferred.

Illustrative examples of the acid labile group of formula (L4) are givenbelow

Examples of the tertiary C₄-C₂₀ alkyl groups, trialkylsilyl groups inwhich each alkyl moiety has 1 to 6 carbon atoms, and C₄-C₂₀ oxoalkylgroups, represented by R⁰¹⁵, are as exemplified for R^(L04) and thelike.

In formula (R2), R⁰¹⁶ is hydrogen or methyl. R⁰¹⁷ is a straight,branched or cyclic C₁-C₈ alkyl group.

In formulae (R1) and (R2), letters all, a2′, a3′, b1′, b2′, b3′, c1′,c2′, c3′, d1′, d2′, d3′, and e′ are numbers from 0 to less than 1,satisfying a1′+a2′+a3′+b1′+b2′+b3′+c1′+c2′+c3′+d1′+d2′+d3′+e′=1; f′, g′,h′, i′, j′, o′, and p′ are numbers from 0 to less than 1, satisfyingf′+g′+h′+i′+j′+o′+p′=1; x′, y′ and z′ are each an integer of 0 to 3,satisfying 1≦x′+y′+z′≦5 and 1≦y′+z′≦3.

With respect to the recurring units of formula (R1) and (R2), units ofmore than one type may be incorporated at the same time. Incorporationof units of more than one type enables to adjust the performance of aresist material in which the resulting polymer is formulated.

Understandably, the sum of respective units=1 means that in a polymercomprising recurring units, the total of the indicated recurring unitsis 100 mol % relative to the total of entire recurring units.

Examples of the recurring units incorporated at compositional ratio a1′in formula (R1) and the recurring units incorporated at compositionalratio f′ in formula (R2) are given below, but not limited thereto.

Examples of the recurring units incorporated at compositional ratio b1′in formula (R1) are given below, but not limited thereto.

Examples of the recurring units incorporated at compositional ratio d1′in formula (R1) and the recurring units incorporated at compositionalratio g′ in formula (R2) are given below, but not limited thereto.

Exemplary polymers comprising recurring units incorporated atcompositional ratios a1′, b1′, c1′, and d1′ in formula (R1) are shownbelow, but not limited thereto.

Exemplary polymers comprising recurring units incorporated atcompositional ratios a2′, b2′, c2′, d2′ and e′ in formula (R1) are shownbelow, but not limited thereto.

Exemplary polymers comprising recurring units incorporated atcompositional ratios a3′, b3′, c3′, and d3′ in formula (R1) are shownbelow, but not limited thereto.

Examples of polymers having formula (R2) are shown below, but notlimited thereto.

The other polymer is blended in an amount of preferably 0 to 80 parts,more preferably 0 to 60 parts, and even more preferably 0 to 50 parts byweight, provided that the total of the resin component (A) and the otherpolymer is 100 parts by weight. When blended, the amount of the otherpolymer is preferably at least 20 parts, more preferably at least 30parts by weight. Too much amounts of the other polymer may prevent theresin component (A) from exerting its own effect, probably resulting ina lower resolution and degraded pattern profile. The other polymer isnot limited to one type and a mixture of two or more other polymers maybe added. The use of plural polymers allows for easy adjustment ofresist properties.

Acid Generator

As the compound which generates an acid in response to actinic light orradiation (B), the resist composition of the invention may furthercomprise (B′) such a compound other than the sulfonium compound offormula (2). Component (B′) may be any compound which generates an acidupon exposure to high-energy radiation and specifically, any ofwell-known photoacid generators which are commonly used in prior artresist compositions, especially chemically amplified resistcompositions. Suitable photoacid generators include sulfonium salts,iodonium salts, sulfonyldiazomethane, N-sulfonyloxyimide, andoxime-O-sulfonate acid generators. Exemplary acid generators are givenbelow while they may be used alone or in admixture of two or more.

Sulfonium salts are salts of sulfonium cations with sulfonates,bis(substituted alkylsulfonyl)imides and tris(substitutedalkylsulfonyl)methides. Exemplary sulfonium cations includetriphenylsulfonium, (4-tert-butoxyphenyl)diphenylsulfonium,bis(4-tert-butoxyphenyl)phenylsulfonium,tris(4-tert-butoxyphenyl)sulfonium,(3-tert-butoxyphenyl)diphenylsulfonium,bis(3-tert-butoxyphenyl)phenylsulfonium,tris(3-tert-butoxyphenyl)sulfonium,(3,4-di-tert-butoxyphenyl)diphenylsulfonium,bis(3,4-di-tert-butoxyphenyl)phenylsulfonium,tris(3,4-di-tert-butoxyphenyl)sulfonium,diphenyl(4-thiophenoxyphenyl)sulfonium,(4-tert-butoxycarbonylmethyloxyphenyl)diphenylsulfonium,tris(4-tert-butoxycarbonylmethyloxyphenyl)sulfonium,(4-tert-butoxyphenyl)bis(4-dimethylaminophenyl)sulfonium,tris(4-dimethylaminophenyl)sulfonium, 2-naphthyldiphenylsulfonium,dimethyl-2-naphthylsulfonium, 4-hydroxyphenyldimethylsulfonium,4-methoxyphenyldimethylsulfonium, trimethylsulfonium,2-oxocyclohexylcyclohexylmethylsulfonium, trinaphthylsulfonium,tribenzylsulfonium, diphenylmethylsulfonium, dimethylphenylsulfonium,2-oxo-2-phenylethylthiacyclopentanium,4-n-butoxynaphthyl-1-thiacyclopentanium, and2-n-butoxynaphthyl-1-thiacyclopentanium. Exemplary sulfonates includetritluoromethanesulfonate, pentafluoroethanesulfonate,nonafluorobutanesulfonate, dodecafluorohexanesulfonate,pentafluoroethylperfluorocyclohexanesulfonate,heptadecafluorooctanesulfonate, 2,2,2-trifluoroethanesulfonate,pentafluorobenzenesulfonate, 4-trifluoromethylbenzenesulfonate,4-fluorobenzenesulfonate, mesitylenesulfonate,2,4,6-triisopropylbenzenesulfonate, toluenesulfonate, benzenesulfonate,4-(4′-toluenesulfonyloxy)benzenesulfonate, naphthalenesulfonate,camphorsulfonate, octanesulfonate, dodecylbenzenesulfonate,butanesulfonate, methanesulfonate,2-benzoyloxy-1,1,3,3,3-pentafluoropropanesulfonate,1,1,3,3,3-pentafluoro-2-(4-phenylbenzoyloxy)propanesulfonate,1,1,3,3,3-pentafluoro-2-pivaloyloxypropanesulfonate,2-cyclohexanecarbonyloxy-1,1,3,3,3-pentafluoropropanesulfonate,1,1,3,3,3-pentafluoro-2-furoyloxypropanesulfonate,2-naphthoyloxy-1,1,3,3,3-pentafluoropropanesulfonate,2-(4-tert-butylbenzoyloxy)-1,1,3,3,3-pentafluoropropanesulfonate,2-adamantanecarbonyloxy-1,1,3,3,3-pentafluoropropanesulfonate,2-acetyloxy-1,1,3,3,3-pentafluoropropanesulfonate,1,1,3,3,3-pentafluoro-2-hydroxypropanesulfonate,1,1,3,3,3-pentafluoro-2-tosyloxypropanesulfonate,1,1-difluoro-2-naphthyl-ethanesulfonate,1,1,2,2-tetrafluoro-2-(norbornan-2-yl)ethanesulfonate, and1,1,2,2-tetrafluoro-2-(tetracyclo[6.2.1.1^(3,6).0^(2,7)]dodec-3-en-8-yl)ethanesulfonate.Exemplary bis(substituted alkylsulfonyl)imides includebistrifluoromethylsulfonylimide, bispentafluoroethylsulfonylimide,bisheptafluoropropylsulfonylimide, and 1,3-propylenebissulfonylimide. Atypical tris(substituted alkylsulfonyl)methide istristrifluoromethylsulfonylmethide. Sulfonium salts based on combinationof the foregoing examples are included.

Iodonium salts are salts of iodonium cations with sulfonates,bis(substituted alkylsulfonyl)imides and tris(substitutedalkylsulfonyl)methides. Exemplary iodonium cations are aryliodoniumcations including diphenyliodinium, bis(4-tert-butylphenyl)iodonium,4-tert-butoxyphenylphenyliodonium, and 4-methoxyphenylphenyliodonium.Exemplary sulfonates include trifluoromethanesulfonate,pentafluoroethanesulfonate, nonafluorobutanesulfonate,dodecafluorohexanesulfonate,pentafluoroethylperfluorocyclohexanesulfonate,heptadecafluorooctanesulfonate, 2,2,2-trifluoroethanesulfonate,pentafluorobenzenesulfonate, 4-trifluoromethylbenzenesulfonate,4-fluorobenzenesulfonate, mesitylenesulfonate,2,4,6-triisopropylbenzenesulfonate, toluenesulfonate, benzenesulfonate,4-(4-toluenesulfonyloxy)benzenesulfonate, naphthalenesulfonate,camphorsulfonate, octanesulfonate, dodecylbenzenesulfonate,butanesulfonate, methanesulfonate,2-benzoyloxy-1,1,3,3,3-pentafluoropropanesulfonate,1,1,3,3,3-pentafluoro-2-(4-phenylbenzoyloxy)propanesulfonate,1,1,3,3,3-pentafluoro-2-pivaloyloxypropanesulfonate,2-cyclohexanecarbonyloxy-1,1,3,3,3-pentafluoropropanesulfonate,1,1,3,3,3-pentafluoro-2-furoyloxypropanesulfonate,2-naphthoyloxy-1,1,3,3,3-pentafluoropropanesulfonate,2-(4-tert-butylbenzoyloxy)-1,1,3,3,3-pentafluoropropanesulfonate,2-adamantanecarbonyloxy-1,1,3,3,3-pentafluoropropanesulfonate,2-acetyloxy-1,1,3,3,3-pentafluoropropanesulfonate,1,1,3,3,3-pentafluoro-2-hydroxypropanesulfonate,1,1,3,3,3-pentafluoro-2-tosyloxypropanesulfonate,1,1-difluoro-2-naphthyl-ethanesulfonate,1,1,2,2-tetrafluoro-2-(norbornan-2-yl)ethanesulfonate, and1,1,2,2-tetrafluoro-2-(tetracyclo[6.2.1.1^(3,6).0^(2,7)]dodec-3-en-8-yl)ethanesulfonate. Exemplary bis(substitutedalkylsulfonyl)imides include bistrifluoromethylsulfonylimide,bispentafluoroethylsulfonylimide, bisheptafluoropropylsulfonylimide, and1,3-propylenebissulfonylimide. A typical tris(substitutedalkylsulfonyl)methide is tristrifluoromethylsulfonylmethide. lodoniumsalts based on combination of the foregoing examples are included.

Exemplary sulfonyldiazomethane compounds include bissulfonyldiazomethanecompounds and sulfonylcarbonyldiazomethane compounds such asbis(ethylsulfonyl)diazomethane, bis(1-methylpropylsulfonyl)diazomethane,bis(2-methylpropylsulfonyl)diazomethane,bis(1,1-dimethylethylsulfonyl)diazomethane,bis(cyclohexylsulfonyl)diazomethane,bis(perfluoroisopropylsulfonyl)diazomethane,bis(phenylsulfonyl)diazomethane,bis(4-methylphenylsulfonyl)diazomethane,bis(2,4-dimethylphenylsulfonyl)diazomethane,bis(2-naphthylsulfonyl)diazomethane,bis(4-acetyloxyphenylsulfonyl)diazomethane,bis(4-methanesulfonyloxyphenylsulfonyl)diazomethane,bis(4-(4-toluenesulfonyloxy)phenylsulfonyl)diazomethane,bis(4-(n-hexyloxy)phenylsulfonyl)diazomethane,bis(2-methyl-4-(n-hexyloxy)phenylsulfonyl)diazomethane,bis(2,5-dimethyl-4-(n-hexyloxy)phenylsulfonyl)diazomethane,bis(3,5-dimethyl-4-(n-hexyloxy)phenylsulfonyl)diazomethane,bis(2-methyl-5-isopropyl-4-(n-hexyloxy)phenylsulfonyl)diazomethane,4-methylphenylsulfonylbenzoyldiazomethane,tert-butylcarbonyl-4-methylphenylsulfonyldiazomethane,2-naphthylsulfonylbenzoyldiazomethane,4-methylphenylsulfonyl-2-naphthoyldiazomethane,methylsulfonylbenzoyldiazomethane, andtert-butoxycarbonyl-4-methylphenylsulfonyldiazomethane.

N-sulfonyloxyimide photoacid generators include combinations of imidestructures with sulfonates. Exemplary imide structures are succinimide,naphthalene dicarboxylic acid imide, phthalimide, cyclohexyldicarboxylicacid imide, 5-norbornene-2,3-dicarboxylic acid imide, and7-oxabicyclo[2.2.1]-5-heptene-2,3-dicarboxylic acid imide. Exemplarysulfonates include trifluoromethanesulfonate,pentafluoroethanesulfonate, nonafluorobutanesulfonate,dodecafluorohexanesulfonate,pentafluoroethylperfluorocyclohexanesulfonate,heptadecafluorooctanesulfonate, 2,2,2-trifluoroethanesulfonate,pentafluorobenzenesulfonate, 4-trifluoromethylbenzenesulfonate,4-fluorobenzenesulfonate, mesitylenesulfonate,2,4,6-triisopropylbenzenesulfonate, toluenesulfonate, benzenesulfonate,naphthalenesulfonate, camphorsulfonate, octanesulfonate,dodecylbenzenesulfonate, butanesulfonate, methanesulfonate,2-benzoyloxy-1,1,3,3,3-pentafluoropropanesulfonate,1,1,3,3,3-pentafluoro-2-(4-phenylbenzoyloxy)propanesulfonate,1,1,3,3,3-pentafluoro-2-pivaloyloxypropanesulfonate,2-cyclohexanecarbonyloxy-1,1,3,3,3-pentafluoropropanesulfonate,1,1,3,3,3-pentafluoro-2-furoyloxypropanesulfonate,2-naphthoyloxy-1,1,3,3,3-pentafluoropropanesulfonate,2-(4-tert-butylbenzoyloxy)-1,1,3,3,3-pentafluoropropanesulfonate,2-adamantanecarbonyloxy-1,1,3,3,3-pentafluoropropanesulfonate,2-acetyloxy-1,1,3,3,3-pentafluoropropanesulfonate,1,1,3,3,3-pentafluoro-2-hydroxypropanesulfonate,1,1,3,3,3-pentafluoro-2-tosyloxypropanesulfonate,1,1-difluoro-2-naphthyl-ethanesulfonate,1,1,2,2-tetrafluoro-2-(norbornan-2-yl)ethanesulfonate, and1,1,2,2-tetrafluoro-2-(tetracyclo[6.2.1.1^(3,6).0^(2,7)]dodec-3-en-8-yl)ethanesulfonate.

Benzoinsulfonate photoacid generators include benzoin tosylate, benzoinmesylate, and benzoin butanesulfonate.

Pyrogallol trisulfonate photoacid generators include pyrogallol,phloroglucinol, catechol, resorcinol, and hydroquinone, in which all thehydroxyl groups are substituted by trifluoromethanesulfonate,pentafluoroethanesulfonate, nonafluorobutanesulfonate,dodecafluorohexanesulfonate,pentafluoroethylperfluorocyclohexanesulfonate,heptadecafluorooctanesulfonate, 2,2,2-trifluoroethanesulfonate,pentafluorobenzenesulfonate, 4-trifluoromethylbenzenesulfonate,4-fluorobenzenesulfonate, toluenesulfonate, benzenesulfonate,naphthalenesulfonate, camphorsulfonate, octanesulfonate,dodecylbenzenesulfonate, butanesulfonate, methanesulfonate,2-benzoyloxy-1,1,3,3,3-pentafluoropropanesulfonate,1,1,3,3,3-pentafluoro-2-(4-phenylbenzoyloxy)propanesulfonate,1,1,3,3,3-pentafluoro-2-pivaloyloxypropanesulfonate,2-cyclohexanecarbonyloxy-1,1,3,3,3-pentafluoropropanesulfonate,1,1,3,3,3-pentafluoro-2-furoyloxypropanesulfonate,2-naphthoyloxy-1,1,3,3,3-pentafluoropropanesulfonate,2-(4-tert-butylbenzoyloxy)-1,1,3,3,3-pentafluoropropanesulfonate,2-adamantanecarbonyloxy-1,1,3,3,3-pentafluoropropanesulfonate,2-acetyloxy-1,1,3,3,3-pentafluoropropanesulfonate,1,1,3,3,3-pentafluoro-2-hydroxypropanesulfonate,1,1,3,3,3-pentafluoro-2-tosyloxypropanesulfonate,1,1-difluoro-2-naphthyl-ethanesulfonate,1,1,2,2-tetrafluoro-2-(norbornan-2-yl)ethanesulfonate, and1,1,2,2-tetrafluoro-2-(tetracyclo[6.2.1.1^(3,6).0^(2,7)]dodec-3-en-8-yl)ethanesulfonate.

Nitrobenzyl sulfonate photoacid generators include 2,4-dinitrobenzylsulfonates, 2-nitrobenzyl sulfonates, and 2,6-dinitrobenzyl sulfonates,with exemplary sulfonates including trifluoromethanesulfonate,pentafluoroethanesulfonate, nonafluorobutanesulfonate,dodecafluorohexanesulfonate,pentafluoroethylperfluorocyclohexanesulfonate,heptadecafluorooctanesulfonate, 2,2,2-trifluoroethanesulfonate,pentafluorobenzenesulfonate, 4-trifluoromethylbenzenesulfonate,4-fluorobenzenesulfonate, toluenesulfonate, benzenesulfonate,naphthalenesulfonate, camphorsulfonate, octanesulfonate,dodecylbenzenesulfonate, butanesulfonate, methanesulfonate,2-benzoyloxy-1,1,3,3,3-pentafluoropropanesulfonate,1,1,3,3,3-pentafluoro-2-(4-phenylbenzoyloxy)propanesulfonate,1,1,3,3,3-pentafluoro-2-pivaloyloxypropanesulfonate,2-cyclohexanecarbonyloxy-1,1,3,3,3-pentafluoropropanesulfonate,1,1,3,3,3-pentafluoro-2-furoyloxypropanesulfonate,2-naphthoyloxy-1,1,3,3,3-pentafluoropropanesulfonate,2-(4-tert-butylbenzoyloxy)-1,1,3,3,3-pentafluoropropanesulfonate,2-adamantanecarbonyloxy-1,1,3,3,3-pentafluoropropanesulfonate,2-acetyloxy-1,1,3,3,3-pentafluoropropanesulfonate,1,1,3,3,3-pentafluoro-2-hydroxypropanesulfonate,1,1,3,3,3-pentafluoro-2-tosyloxypropanesulfonate,1,1-difluoro-2-naphthyl-ethanesulfonate,1,1,2,2-tetrafluoro-2-(norbornan-2-yl)ethanesulfonate, and1,1,2,2-tetrafluoro-2-(tetracyclo[6.2.1.1^(3,6).0^(2,7)]dodec-3-en-8-yl)ethanesulfonate.Also useful are analogous nitrobenzyl sulfonate compounds in which thenitro group on the benzyl side is substituted by a trifluoromethylgroup.

Sulfone photoacid generators include bis(phenylsulfonyl)methane,bis(4-methylphenylsulfonyl)methane, bis(2-naphthylsulfonyl)methane,2,2-bis(phenylsulfonyl)propane, 2,2-bis(4-methylphenylsulfonyl)propane,2,2-bis(2-naphthylsulfonyl)propane,2-methyl-2-(p-toluenesulfonyl)propiophenone,2-cyclohexylcarbonyl-2-(p-toluenesulfonyl)propane, and2,4-dimethyl-2-(p-toluenesulfonyl)pentan-3-one.

Photoacid generators in the form of glyoxime derivatives are describedin Japanese Patent No. 2,906,999 and JP-A 9-301948 and includebis-O-(p-toluenesulfonyl)-α-dimethylglyoxime,bis-O-(p-toluenesulfonyl)-α-diphenylglyoxime,bis-O-(p-toluenesulfonyl)-α-dicyclohexylglyoxime,bis-O-(p-toluenesulfonyl)-2,3-pentanedioneglyoxime,bis-O-(n-butanesulfonyl)-α-dimethylglyoxime,bis-O-(n-butanesulfonyl)-α-diphenylglyoxime,bis-O-(n-butanesulfonyl)-α-dicyclohexylglyoxime,bis-O-(methanesulfonyl)-α-dimethylglyoxime,bis-O-(trifluoromethanesulfonyl)-α-dimethylglyoxime,bis-O-(2,2,2-trifluoroethanesulfonyl)-α-dimethylglyoxime,bis-O-(10-camphorsulfonyl)-α-dimethylglyoxime,bis-O-(benzenesulfonyl)-α-dimethylglyoxime,bis-O-(p-fluorobenzenesulfonyl)-α-dimethylglyoxime,bis-O-(p-trifluoromethylbenzenesulfonyl)-α-dimethylglyoxime,bis-O-(xylenesulfonyl)-α-dimethylglyoxime,bis-O-(trifluoromethanesulfonyl)-nioxime,bis-O-(2,2,2-trifluoroethanesulfonyl)-nioxime,bis-O-(10-camphorsulfonyl)-nioxime, bis-O-(benzenesulfonyl)-nioxime,bis-O-(p-fluorobenzenesulfonyl)-nioxime,bis-O-(p-trifluoromethylbenzenesulfonyl)-nioxime, andbis-O-(xylenesulfonyl)-nioxime.

Also included are the oxime sulfonates described in U.S. Pat. No.6,004,724, for example,(5-(4-toluenesulfonyl)oxyimino-5H-thiophen-2-ylidene)phenylacetonitrile,(5-(10-camphorsulfonyl)oxyimino-5H-thiophen-2-ylidene)phenylacetonitrile,(5-n-octanesulfonyloxyimino-5H-thiophen-2-ylidene)phenylacetonitrile,(5-(4-toluenesulfonyl)oxyimino-5H-thiophen-2-ylidene)(2-methylphenyl)acetonitrile,(5-(10-camphorsulfonyl)oxyimino-5H-thiophen-2-ylidene)(2-methylphenyl)acetonitrile,(5-n-octanesulfonyloxyimino-5H-thiophen-2-ylidene)(2-methylphenyl)acetonitrile,etc. Also included are the oxime sulfonates described in U.S. Pat. No.6,916,591, for example,(5-(4-(4-toluenesulfonyloxy)benzenesulfonyl)oxyimino-5H-thiophen-2-ylidene)phenylacetonitrileand(5-(2,5-bis(4-toluenesulfonyloxy)benzenesulfonyl)oxyimino-5H-thiophen-2-ylidene)phenylacetonitrile.

Also included are the oxime sulfonates described in U.S. Pat. No.6,261,738 and JP-A 2000-314956, for example,2,2,2-trifluoro-1-phenyl-ethanone oxime-O-methylsulfonate;2,2,2-trifluoro-1-phenyl-ethanone oxime-O-(10-camphoryl-sulfonate);2,2,2-trifluoro-1-phenyl-ethanone oxime-O-(4-methoxyphenylsulfonate);2,2,2-trifluoro-1-phenyl-ethanone oxime-O-(1-naphthylsulfonate);2,2,2-trifluoro-1-phenyl-ethanone oxime-O-(2-naphthylsulfonate);2,2,2-trifluoro-1-phenyl-ethanoneoxime-O-(2,4,6-trimethylphenylsulfonate);2,2,2-trifluoro-1-(4-methylphenyl)-ethanoneoxime-O-(10-camphorylsulfonate);2,2,2-trifluoro-1-(4-methylphenyl)-ethanone oxime-O-(methylsulfonate);2,2,2-trifluoro-1-(2-methylphenyl)-ethanoneoxime-O-(10-camphorylsulfonate);2,2,2-trifluoro-1-(2,4-dimethylphenyl)-ethanoneoxime-O-(10-camphorylsulfonate);2,2,2-trifluoro-1-(2,4-dimethylphenyl)-ethanoneoxime-O-(1-naphthylsulfonate);2,2,2-trifluoro-1-(2,4-dimethylphenyl)-ethanoneoxime-O-(2-naphthylsulfonate);2,2,2-trifluoro-1-(2,4,6-trimethylphenyl)-ethanoneoxime-O-(10-camphorylsulfonate);2,2,2-trifluoro-1-(2,4,6-trimethylphenyl)-ethanoneoxime-O-(1-naphthylsulfonate);2,2,2-trifluoro-1-(2,4,6-trimethylphenyl)-ethanoneoxime-O-(2-naphthylsulfonate);2,2,2-trifluoro-1-(4-methoxyphenyl)-ethanone oxime-O-methylsulfonate;2,2,2-trifluoro-1-(4-methylthiophenyl)-ethanone oxime-O-methylsulfonate;2,2,2-trifluoro-1-(3,4-dimethoxyphenyl)-ethanoneoxime-O-methylsulfonate; 2,2,3,3,4,4,4-heptafluoro-1-phenyl-butanoneoxime-O-(10-camphorylsulfonate); 2,2,2-trifluoro-1-(phenyl)-ethanoneoxime-O-methylsulfonate; 2,2,2-trifluoro-1-(phenyl)-ethanoneoxime-O-10-camphorylsulfonate; 2,2,2-trifluoro-1-(phenyl)-ethanoneoxime-O-(4-methoxyphenyl)sulfonate; 2,2,2-trifluoro-1-(phenyl)-ethanoneoxime-O-(1-naphthyl)-sulfonate; 2,2,2-trifluoro-1-(phenyl)-ethanoneoxime-O-(2-naphthyl)sulfonate; 2,2,2-trifluoro-1-(phenyl)-ethanoneoxime-O-(2,4,6-trimethylphenyl)sulfonate;2,2,2-trifluoro-1-(4-methylphenyl)-ethanoneoxime-O-(10-camphoryl)sulfonate;2,2,2-trifluoro-1-(4-methylphenyl)-ethanone oxime-O-methylsulfonate;2,2,2-trifluoro-1-(2-methylphenyl)-ethanoneoxime-O-(10-camphoryl)sulfonate;2,2,2-triflubro-1-(2,4-dimethyl-phenyl)-ethanoneoxime-O-(1-naphthyl)sulfonate;2,2,2-trifluoro-1-(2,4-dimethylphenyl)-ethanoneoxime-O-(2-naphthyl)sulfonate;2,2,2-trifluoro-1-(2,4,6-trimethylphenyl)-ethanoneoxime-O-(10-camphoryl)sulfonate;2,2,2-trifluoro-1-(2,4,6-trimethylphenyl)-ethanoneoxime-O-(1-naphthyl)sulfonate;2,2,2-trifluoro-1-(2,4,6-trimethylphenyl)-ethanoneoxime-O-(2-naphthyl)sulfonate;2,2,2-trifluoro-1-(4-methoxyphenyl)-ethanone oxime-O-methylsulfonate;2,2,2-trifluoro-1-(4-thiomethylphenyl)-ethanone oxime-O-methylsulfonate;2,2,2-trifluoro-1-(3,4-dimethoxyphenyl)-ethanoneoxime-O-methylsulfonate; 2,2,2-trifluoro-1-(4-methoxyphenyl)-ethanoneoxime-O-(4-methylphenyl)sulfonate;2,2,2-trifluoro-1-(4-methoxyphenyl)-ethanoneoxime-O-(4-methoxyphenyl)sulfonate;2,2,2-trifluoro-1-(4-methoxyphenyl)-ethanoneoxime-O-(4-dodecylphenyl)-sulfonate;2,2,2-trifluoro-1-(4-methoxyphenyl)-ethanone oxime-O-octylsulfonate;2,2,2-trifluoro-1-(4-thiomethyl-phenyl)-ethanoneoxime-O-(4-methoxyphenyl)sulfonate;2,2,2-trifluoro-1-(4-thiomethylphenyl)-ethanoneoxime-O-(4-dodecylphenyl)sulfonate;2,2,2-trifluoro-1-(4-thiomethyl-phenyl)-ethanone oxime-O-octylsulfonate;2,2,2-trifluoro-1-(4-thiomethylphenyl)-ethanoneoxime-O-(2-naphthyl)sulfonate;2,2,2-trifluoro-1-(2-methylphenyl)-ethanone oxime-O-methylsulfonate;2,2,2-trifluoro-1-(4-methylphenyl)ethanone oxime-O-phenylsulfonate;2,2,2-trifluoro-1-(4-chlorophenyl)-ethanone oxime-O-phenylsulfonate;2,2,3,3,4,4,4-heptafluoro-1-(phenyl)-butanoneoxime-O-(10-camphoryl)sulfonate; 2,2,2-trifluoro-1-naphthyl-ethanoneoxime-O-methylsulfonate; 2,2,2-trifluoro-2-naphthyl-ethanoneoxime-O-methylsulfonate; 2,2,2-trifluoro-1-[4-benzylphenyl]-ethanoneoxime-O-methylsulfonate;2,2,2-trifluoro-1-[4-(phenyl-1,4-dioxa-but-1-yl)phenyl]-ethanoneoxime-O-methylsulfonate; 2,2,2-trifluoro-1-naphthyl-ethanoneoxime-O-propylsulfonate; 2,2,2-trifluoro-2-naphthyl-ethanoneoxime-O-propylsulfonate; 2,2,2-trifluoro-1-[4-benzylphenyl]-ethanoneoxime-O-propylsulfonate;2,2,2-trifluoro-1-[4-methylsulfonylphenyl]-ethanoneoxime-O-propylsulfonate;1,3-bis[1-(4-phenoxyphenyl)-2,2,2-trifluoro-ethanoneoxime-O-sulfonyl]phenyl;2,2,2-trifluoro-1-[4-methylsulfonyloxyphenyl]-ethanoneoxime-O-propylsulfonate;2,2,2-trifluoro-1-[4-methylcarbonyloxyphenyl]-ethanoneoxime-O-propylsulfonate;2,2,2-trifluoro-1-[6H,7H-5,8-dioxonaphth-2-yl]-ethanoneoxime-O-propylsulfonate;2,2,2-trifluoro-1-[4-methoxycarbonylmethoxyphenyl]-ethanoneoxime-O-propyl-sulfonate;2,2,2-trifluoro-1-[4-(methoxycarbonyl)-(4-amino-1-oxa-pent-1-yl)-phenyl]-ethanoneoxime-O-propylsulfonate;2,2,2-trifluoro-1-[3,5-dimethyl-4-ethoxyphenyl]-ethanoneoxime-O-propylsulfonate; 2,2,2-trifluoro-1-[4-benzyloxy-phenyl]-ethanoneoxime-O-propylsulfonate; 2,2,2-trifluoro-1-[2-thiophenyl]-ethanoneoxime-O-propylsulfonate;2,2,2-trifluoro-1-[1-dioxa-thiophen-2-yl)]-ethanoneoxime-O-propylsulfonate;2,2,2-trifluoro-1-(4-(3-(4-(2,2,2-trifluoro-1-(trifluoromethanesulfonyloxyimino)-ethyl)-phenoxy)-propoxy)-phenyl)ethanoneoxime(trifluoromethanesulfonate);2,2,2-trifluoro-1-(4-(3-(4-(2,2,2-trifluoro-1-(1-propanesulfonyloxyimino)-ethyl)-phenoxy)-propoxy)-phenyl)ethanoneoxime(1-propanesulfonate); and2,2,2-trifluoro-1-(4-(3-(4-(2,2,2-trifluoro-1-(1-butanesulfonyloxyimino)-ethyl)-phenoxy)-propoxy)-phenyl)ethanoneoxime(1-butanesulfonate). Also included are the oxime sulfonatesdescribed in U.S. Pat. No. 6,916,591, for example,2,2,2-trifluoro-1-(4-(3-(4-(2,2,2-trifluoro-1-(4-(4-methylphenylsulfonyloxy)phenylsulfonyloxyimino)-ethyl)-phenoxy)-propoxy)-phenyl)ethanoneoxime(4-(4-methylphenylsulfonyloxy)phenylsulfonate) and2,2,2-trifluoro-1-(4-(3-(4-(2,2,2-trifluoro-1-(2,5-bis(4-methylphenylsulfonyloxy)benzenesulfonyloxy)phenylsulfonyloxyimino)-ethyl)-phenoxy)-propoxy)-phenyl)ethanoneoxime(2,5-bis(4-methylphenylsulfonyloxy)benzenesulfonyloxy)phenylsulfonate).

Also included are the oxime sulfonates described in JP-A 9-95479 andJP-A 9-230588 and the references cited therein, for example,α-(p-toluenesulfonyloxyimino)-phenylacetonitrile,α-(p-chlorobenzenesulfonyloxyimino)-phenylacetonitrile,α-(4-nitrobenzenesulfonyloxyimino)-phenylacetonitrile,α-(4-nitro-2-trifluoromethylbenzenesulfonyloxyimino)-phenylacetonitrile,α-(benzenesulfonyloxyimino)-4-chlorophenylacetonitrile,α-(benzenesulfonyloxyimino)-2,4-dichlorophenylacetonitrile,α-(benzenesulfonyloxyimino)-2,6-dichlorophenylacetonitrile,α-(benzenesulfonyloxyimino)-4-methoxyphenylacetonitrile,α-(2-chlorobenzenesulfonyloxyimino)-4-methoxyphenylacetonitrile,α-(benzenesulfonyloxyimino)-2-thienylacetonitrile,α-(4-dodecylbenzenesulfonyloxyimino)-phenylacetonitrile,α-[(4-toluenesulfonyloxyimino)-4-methoxyphenyl]acetonitrile,α-[(dodecylbenzenesulfonyloxyimino)-4-methoxyphenyl]acetonitrile,α-(tosyloxyimino)-3-thienylacetonitrile,α-(methylsulfonyloxyimino)-1-cyclopentenylacetonitrile,α-(ethylsulfonyloxyimino)-1-cyclopentenylacetonitrile,α-(isopropylsulfonyloxyimino)-1-cyclopentenylacetonitrile,α-(n-butylsulfonyloxyimino)-1-cyclopentenylacetonitrile,α-(ethylsulfonyloxyimino)-1-cyclohexenylacetonitrile,α-(isopropylsulfonyloxyimino)-1-cyclohexenylacetonitrile, andα-(n-butylsulfonyloxyimino)-1-cyclohexenylacetonitrile.

Also included are oxime sulfonates having the formula:

wherein R^(s1) is a substituted or unsubstituted haloalkylsulfonyl orhalobenzenesulfonyl group of 1 to 10 carbon atoms, R^(s2) is a haloalkylgroup of 1 to 11 carbon atoms, and Ar^(s1) is substituted orunsubstituted aromatic or hetero-aromatic group, examples of which aredescribed, for example, in WO 2004/074242.

Examples include2-[2,2,3,3,4,4,5,5-octafluoro-1-(nonafluorobutylsulfonyloxyimino)-pentyl]-fluorene,2-[2,2,3,3,4,4-pentafluoro-1-(nonafluorobutylsulfonyloxyimino)-butyl]-fluorene,2-[2,2,3,3,4,4,5,5,6,6-decafluoro-1-(nonafluorobutylsulfonyloxyimino)-hexyl]-fluorene,2-[2,2,3,3,4,4,5,5-octafluoro-1-(nonafluorobutylsulfonyloxyimino)-pentyl]-4-biphenyl,2-[2,2,3,3,4,4-pentafluoro-1-(nonafluorobutylsulfonyloxyimino)-butyl]-4-biphenyl,and2-[2,2,3,3,4,4,5,5,6,6-decafluoro-1-(nonafluorobutylsulfonyloxyimino)-hexyl]-4-biphenyl.

Suitable bisoxime sulfonates include those described in JP-A 9-208554,for example,bis(α-(4-toluenesulfonyloxy)imino)-p-phenylenediacetonitrile,bis(α-(benzenesulfonyloxy)imino)-p-phenylenediacetonitrile,bis(α-(methanesulfonyloxy)imino)-p-phenylenediacetonitrile,bis(α-(butanesulfonyloxy)imino)-p-phenylenediacetonitrile,bis(α-(10-camphorsulfonyloxy)imino)-p-phenylenediacetonitrile,bis(α-(4-toluenesulfonyloxy)imino)-p-phenylenediacetonitrile,bis(α-(trifluoromethanesulfonyloxy)imino)-p-phenylenediacetonitrile,bis(α-(4-methoxybenzenesulfonyloxy)imino)-p-phenylenediacetonitrile,bis(α-(4-toluenesulfonyloxy)imino)-m-phenylenediacetonitrile,bis(α-(benzenesulfonyloxy)imino)-m-phenylenediacetonitrile,bis(α-(methanesulfonyloxy)imino)-m-phenylenediacetonitrile,bis(α-(butanesulfonyloxy)imino)-m-phenylenediacetonitrile,bis(α-(10-camphorsulfonyloxy)imino)-m-phenylenediacetonitrile,bis(α-(4-toluenesulfonyloxy)imino)-m-phenylenediacetonitrile,bis(α-(trifluoromethanesulfonyloxy)imino)-m-phenylenediacetonitrile,bis(α-(4-methoxybenzenesulfonyloxy)imino)-m-phenylenediacetonitrile,etc.

Of these, preferred photoacid generators are sulfonlum salts,bissulfonyldiazomethanes, N-sulfonyloxyimides, oxime-O-sulfonates andglyoxime derivatives. More preferred photoacid generators are sulfoniumsalts, bissulfonyldiazomethanes, N-sulfonyloxyimides, andoxime-O-sulfonates. Typical examples include triphenylsulfoniump-toluenesulfonate, triphenylsulfonium camphorsulfonate,triphenylsulfonium pentafluorobenzenesulfonate, triphenylsulfoniumnonafluorobutanesulfonate, triphenylsulfonium4-(4′-toluenesulfonyloxy)benzenesulfonate, triphenylsulfonium2,4,6-triisopropylbenzenesulfonate, 4-tert-butoxyphenyldiphenylsulfoniump-toluenesulfonate, 4-tert-butoxyphenyldiphenylsulfoniumcamphorsulfonate, 4-tert-butoxyphenyldiphenylsulfonium4-(4′-toluenesulfonyloxy)benzenesulfonate, tris(4-methylphenyl)sulfoniumcamphorsulfonate, tris(4-tert-butylphenyl)sulfonium camphorsulfonate,4-tert-butylphenyldiphenylsulfonium camphorsulfonate,4-tert-butylphenyldiphenylsulfonium nonafluoro-1-butanesulfonate,4-tert-butylphenyldiphenylsulfoniumpentafluoroethyl-perfluorocyclohexanesulfonate,4-tert-butylphenyldiphenylsulfonium perfluoro-1-octanesulfonate,triphenylsulfonium 1,1-difluoro-2-naphthyl-ethanesulfonate,triphenylsulfonium1,1,2,2-tetrafluoro-2-(norbornan-2-yl)ethanesulfonate,bis(tert-butylsulfonyl)diazomethane,bis(cyclohexylsulfonyl)diazomethane,bis(2,4-dimethylphenylsulfonyl)diazomethane,bis(4-(n-hexyloxy)phenylsulfonyl)diazomethane,bis(2-methyl-4-(n-hexyloxy)phenylsulfonyl)diazomethane,bis(2,5-dimethyl-4-(n-hexyloxy)phenylsulfonyl)diazomethane,bis(3,5-dimethyl-4-(n-hexyloxy)phenylsulfonyl)diazomethane,bis(2-methyl-5-isopropyl-4-(n-hexyloxy)phenylsulfonyl)diazomethane,bis(4-tert-butylphenylsulfonyl)diazomethane,N-camphorsulfonyloxy-5-norbornene-2,3-dicarboxylic acid imide,N-p-toluenesulfonyloxy-5-norbornene-2,3-dicarboxylic acid imide,2-[2,2,3,3,4,4,5,5-octafluoro-1-(nonafluorobutylsulfonyloxyimino)-pentyl]-fluorene,2-[2,2,3,3,4,4-pentafluoro-1-(nonafluorobutylsulfonyloxyimino)-butyl]-fluorene,and2-[2,2,3,3,4,4,5,5,6,6-decafluoro-1-(nonafluorobutylsulfonyloxyimino)-hexyl]-fluorene.

In the resist composition, an appropriate amount of the photoacidgenerators (B) and (B′) is, but not limited to, 0.1 to 40 parts, andespecially 0.1 to 20 parts by weight per 100 parts by weight of the basepolymer (i.e., resin component (A) and optional other resin component).Too high a proportion of the photoacid generators may give rise toproblems of degraded resolution and foreign matter upon development andresist film peeling. Provided that [B] and [B′] stand for the amounts ofgenerators (B) and (B′) added, respectively, the preferred blendingproportion of generators (B) and (B′) is 0.1≦[B]/([B]+[B′])≦1, morepreferably 0.3≦[B]/([B]+[B′])≦1, and even more preferably0.5≦[B]/([B]+[B′])≦1. If a blending proportion of generator (B) is toolow, then exposure dose dependency, pattern density dependency and/ormask fidelity may be degraded. The photoacid generators (B) and (B′)each may be used alone or in admixture of two or more. The transmittanceof the resist film can be controlled by using a photoacid generatorhaving a low transmittance at the exposure wavelength and adjusting theamount of the photoacid generator added.

In the resist composition, there may be added a compound which isdecomposed with an acid to generate another acid, that is,acid-amplifier compound. For these compounds, reference should be madeto J. Photopolym. Sci. and Tech., 8, 43-44, 45-46 (1995), and ibid., 9,29-30 (1996).

Examples of the acid-amplifier compound includetert-butyl-2-methyl-2-tosyloxymethyl acetoadetate and2-phenyl-2-(2-tosyloxyethyl)-1,3-dioxolane, but are not limited thereto.Of well-known photoacid generators, many of those compounds having poorstability, especially poor thermal stability exhibit an acidamplifier-like behavior.

In the resist composition, an appropriate amount of the acid-amplifiercompound is 0 to 2 parts, and especially 0 to 1 part by weight per 100parts by weight of the base polymer. Excessive amounts of theacid-amplifier compound make diffusion control difficult, leading todegradation of resolution and pattern profile.

In addition to components (A) and (B), the resist composition mayfurther comprise (C) an organic solvent and optionally (D) an organicnitrogen-containing compound, (E) a surfactant, and (F) othercomponents.

Organic Solvent

The organic solvent (C) used herein may be any organic solvent in whichthe base resin, acid generator, and additives are soluble. Illustrative,non-limiting, examples of the organic solvent include ketones such ascyclohexanone and methyl amyl ketone; alcohols such as 3-methoxybutanol,3-methyl-3-methoxybutanol, 1-methoxy-2-propanol, and1-ethoxy-2-propanol; ethers such as propylene glycol monomethyl ether,ethylene glycol monomethyl ether, propylene glycol monoethyl ether,ethylene glycol monoethyl ether, propylene glycol dimethyl ether, anddiethylene glycol dimethyl ether; esters such as propylene glycolmonomethyl ether acetate (PGMEA), propylene glycol monoethyl etheracetate, ethyl lactate, ethyl pyruvate, butyl acetate, methyl3-methoxypropionate, ethyl 3-ethoxypropionate, tert-butyl acetate,tert-butyl propionate, and propylene glycol mono-tert-butyl etheracetate; and lactones such as y-butyrolactone. These solvents may beused alone or in combinations of two or more thereof. Of the aboveorganic solvents, it is recommended to use diethylene glycol dimethylether, 1-ethoxy-2-propanol, propylene glycol monomethyl ether acetate,and mixtures thereof because the acid generator is most soluble therein.

An appropriate amount of the organic solvent used is about 200 to 3,000parts, especially about 400 to 2,500 parts by weight per 100 parts byweight of the base polymer.

Nitrogen-Containing Compound

In the resist composition, an organic nitrogen-containing compound orcompounds may be compounded as component (D). The organicnitrogen-containing compound used herein is preferably a compoundcapable of suppressing the rate of diffusion when the acid generated bythe acid generator diffuses within the resist film. The inclusion oforganic nitrogen-containing compound holds down the rate of aciddiffusion within the resist film, resulting in better resolution. Inaddition, it suppresses changes in sensitivity following exposure andreduces substrate and environment dependence, as well as improving theexposure latitude and the pattern profile.

The organic nitrogen-containing compound used herein may be any ofwell-known organic nitrogen-containing compounds which are commonly usedin prior art resist compositions, especially chemically amplified resistcompositions. Suitable organic nitrogen-containing compounds includeprimary, secondary, and tertiary aliphatic amines, mixed amines,aromatic amines, heterocyclic amines, nitrogen-containing compoundshaving carboxyl group, nitrogen-containing compounds having sulfonylgroup, nitrogen-containing compounds having hydroxyl group,nitrogen-containing compounds having hydroxyphenyl group, alcoholicnitrogen-containing compounds, amide derivatives, imide derivatives, andcarbamate derivatives.

Of the organic nitrogen-containing compounds described above, tertiaryamines are preferably selected as the acid diffusion regulator.

Examples of suitable primary aliphatic amines include ammonia,methylamine, ethylamine, n-propylamine, isopropylamine, n-butylamine,isobutylamine, sec-butylamine, tert-butylamine, pentylamine,tert-amylamine, cyclopentylamine, hexylamine, cyclohexylamine,heptylamine, octylamine, nonylamine, decylamine, dodecylamine,cetylamine, methylenediamine, ethylenediamine, andtetraethylenepentamine. Examples of suitable secondary aliphatic aminesinclude dimethylamine, diethylamine, di-n-propylamine, diisopropylamine,di-n-butylamine, diisobutylamine, di-sec-butylamine, dipentylamine,dicyclopentylamine, dihexylamine, dicyclohexylamine, diheptylamine,dioctylamine, dinonylamine, didecylamine, didodecylamine, dicetylamine,N,N-dimethylmethylenediamine, N,N-dimethylethylenediamine, andN,N-dimethyltetraethylenepentamine. Examples of suitable tertiaryaliphatic amines include trimethylamine, triethylamine,tri-n-propylamine, triisopropylamine, tri-n-butylamine,triisobutylamine, tri-sec-butylamine, tripentylamine,tricyclopentylamine, trihexylamine, tricyclohexylamine, triheptylamine,trioctylamine, trinonylamine, tridecylamine, tridodecylamine,tricetylamine, N,N,N′,N′-tetramethylmethylenediamine,N,N,N′,N′-tetramethylethylenediamine, andN,N,N′,N′-tetramethyltetraethylenepentamine.

Examples of suitable mixed amines include dimethylethylamine,methylethylpropylamine, benzylamine, phenethylamine, andbenzyldimethylamine. Examples of suitable aromatic and heterocyclicamines include aniline derivatives (e.g., aniline, N-methylaniline,N-ethylaniline, N-propylaniline, N,N-dimethylaniline, 2-methylaniline,3-methylaniline, 4-methylaniline, ethylaniline, propylaniline,trimethylaniline, 2-nitroaniline, 3-nitroaniline, 4-nitroaniline,2,4-dinitroaniline, 2,6-dinitroaniline, 3,5-dinitroaniline, andN,N-dimethyltoluidine), diphenyl(p-tolyl)amine, methyldiphenylamine,triphenylamine, phenylenediamine, naphthylamine, diaminonaphthalene,pyrrole derivatives (e.g., pyrrole, 2H-pyrrole, 1-methylpyrrole,2,4-dimethylpyrrole, 2,5-dimethylpyrrole, and N-methylpyrrole), oxazolederivatives (e.g., oxazole and isooxazole), thiazole derivatives (e.g.,thiazole and isothiazole), imidazole derivatives (e.g., imidazole,4-methylimidazole, and 4-methyl-2-phenylimidazole), pyrazolederivatives, furazan derivatives, pyrroline derivatives (e.g., pyrrolineand 2-methyl-1-pyrroline), pyrrolidine derivatives (e.g., pyrrolidine,N-methylpyrrolidine, pyrrolidinone, and N-methylpyrrolidone),imidazoline derivatives, imidazolidine derivatives, pyridine derivatives(e.g., pyridine, methylpyridine, ethylpyridine, propylpyridine,butylpyridine, 4-(1-butylpentyl)pyridine, dimethylpyridine,trimethylpyridine, triethylpyridine, phenylpyridine,3-methyl-2-phenylpyridine, 4-tert-butylpyridine, diphenylpyridine,benzylpyridine, methoxypyridine, butoxypyridine, dimethoxypyridine,4-pyrrolidinopyridine, 2-(1-ethylpropyl)pyridine, aminopyridine, anddimethylaminopyridine), pyridazine derivatives, pyrimidine derivatives,pyrazine derivatives. pyrazoline derivatives, pyrazolidine derivatives,piperidine derivatives, piperazine derivatives, morpholine derivatives,indole derivatives, isoindole derivatives, 1H-indazole derivatives,indoline derivatives, quinoline derivatives (e.g., quinoline and3-quinolinecarbonitrile), isoquinoline derivatives, cinnolinederivatives, quinazoline derivatives, quinoxaline derivatives,phthalazine derivatives, purine derivatives, pteridine derivatives,carbazole derivatives, phenanthridine derivatives, acridine derivatives,phenazine derivatives, 1,10-phenanthroline derivatives, adeninederivatives, adenosine derivatives, guanine derivatives, guanosinederivatives, uracil derivatives, and uridine derivatives.

Examples of suitable nitrogen-containing compounds 1S having carboxylgroup include aminobenzoic acid, indolecarboxylic acid, and amino acidderivatives (e.g. nicotinic acid, alanine, alginine, aspartic acid,glutamic acid, glycine, histidine, isoleucine, glycylleucine, leucine,methionine, phenylalanine, threonine, lysine,3-aminopyrazine-2-carboxylic acid, and methoxyalanine). Examples ofsuitable nitrogen-containing compounds having sulfonyl group include3-pyridinesulfonic acid and pyridinium p-toluenesulfonate. Examples ofsuitable nitrogen-containing compounds having hydroxyl group,nitrogen-containing compounds having hydroxyphenyl group, and alcoholicnitrogen-containing compounds include 2-hydroxypyridine, aminocresol,2,4-quinolinediol, 3-indolemethanol hydrate, monoethanolamine,diethanolamine, triethanolamine, N-ethyldiethanolamine,N,N-diethylethanolamine, triisopropanolamine, 2,2′-iminodiethanol,2-aminoethanol, 3-amino-1-propanol, 4-amino-1-butanol,4-(2-hydroxyethyl)morpholine, 2-(2-hydroxyethyl)pyridine,1-(2-hydroxyethyl)piperazine, 1-[2-(2-hydroxyethoxy)ethyl]piperazine,piperidine ethanol, 1-(2-hydroxyethyl)pyrrolidine,1-(2-hydroxyethyl)-2-pyrrolidinone, 3-piperidino-1,2-propanediol,3-pyrrolidino-1,2-propanediol, 8-hydroxyjulolidine, 3-quinuclidinol,3-tropanol, 1-methyl-2-pyrrolidine ethanol, 1-aziridine ethanol,N-(2-hydroxyethyl)phthalimide, and N-(2-hydroxyethyl)isonicotinamide.Examples of suitable amide derivatives include formamide,N-methylformamide, N,N-dimethylformamide, acetamide, N-methylacetamide,N,N-dimethylacetamide, propionamide, benzamide, and1-cyclohexylpyrrolidone. Suitable imide derivatives include phthalimide,succinimide, and maleimide. Suitable carbamate derivatives includeN-t-butoxycarbonyl-N,N-dicyclohexylamine,N-t-butoxycarbonylbenzimidazole and oxazolidinone.

In addition, organic nitrogen-containing compounds of the followinggeneral formula (B)-1 may also be included alone or in admixture.

N(X)_(n)(Y)_(3-n)   (B)-1

In the formula, n is equal to 1, 2 or 3; side chain Y is independentlyhydrogen or a straight, branched or cyclic C₁-C₂₀ alkyl group which maycontain an ether or hydroxyl group; and side chain X is independentlyselected from groups of the following general formulas (X1) to (X3), andtwo or three X's may bond together to form a ring.

In the formulas, R³⁰⁰, R³⁰² and R³⁰⁵ are independently straight orbranched C₁-C₄ alkylene groups; R³⁰¹ and R³⁰⁴ are independentlyhydrogen, or straight, branched or cyclic C₁-C₂₀ alkyl groups which maycontain at least one hydroxyl, ether, ester group or lactone ring; R³⁰³is a single bond or a straight or branched C₁-C₄ alkylene group; andR³⁰⁶ is a straight, branched or cyclic C₁-C₂₀ alkyl group which maycontain at least one hydroxyl, ether, ester group or lactone ring.

Illustrative examples of the compounds of formula (B)-1 includetris(2-methoxymethoxyethyl)amine, tris{2-(2-methoxyethoxy)ethyl}amine,tris{2-(2-methoxyethoxymethoxy)ethyl}amine,tris{2-(1-methoxyethoxy)ethyl}amine, tris{2-(1-ethoxyethoxy)ethyl}amine,tris{2-(1-ethoxypropoxy)ethyl}amine,tris[2-{2-(2-hydroxyethoxy)ethoxy}ethyl]amine,4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8]hexacosane,4,7,13,18-tetraoxa-1,10-diazabicyclo[8.5.5]eicosane,1,4,10,13-tetraoxa-7,16-diazabicyclooctadecane,1-aza-12-crown-4,1-aza-15-crown-5,1-aza-18-crown-6,tris(2-formyloxyethyl)amine, tris(2-acetoxyethyl)amine,tris(2-propionyloxyethyl)amine, tris(2-butyryloxyethyl)amine,tris(2-isobutyryloxyethyl)amine, tris(2-valeryloxyethyl)amine,tris(2-pivaloyloxyethyl)amine,N,N-bis(2-acetoxyethyl)-2-(acetoxyacetoxy)ethylamine,tris(2-methoxycarbonyloxyethyl)amine,tris(2-tert-butoxycarbonyloxyethyl)amine,tris[2-(2-oxopropoxy)ethyl]amine,tris[2-(methoxycarbonylmethyl)oxyethyl]amine,tris[2-(tert-butoxycarbonylmethyloxy)ethyl]amine,tris[2-(cyclohexyloxycarbonylmethyloxy)ethyl]amine,tris(2-methoxycarbonylethyl)amine, tris(2-ethoxycarbonylethyl)amine,N,N-bis(2-hydroxyethyl)-2-(methoxycarbonyl)ethylamine,N,N-bis(2-acetoxyethyl)-2-(methoxycarbonyl)ethylamine,N,N-bis(2-hydroxyethyl)-2-(ethoxycarbonyl)ethylamine,N,N-bis(2-acetoxvethyl)-2-(ethoxycarbonyl)ethylamine,N,N-bis(2-hydroxyethyl)-2-(2-methoxyethoxycarbonyl)ethylamine,N,N-bis(2-acetoxyethyl)-2-(2-methoxyethoxycarbonyl)ethylamine,N,N-bis(2-hydroxyethyl)-2-(2-hydroxyethoxycarbonyl)ethylamine,N,N-bis(2-acetoxyethyl)-2-(2-acetoxyethoxycarbonyl)ethylamine,N,N-bis(2-hydroxyethyl)-2-[(methoxycarbonyl)methoxycarbonyl]-ethylamine,N,N-bis(2-acetoxyethyl)-2-[(methoxycarbonyl)methoxycarbonyl]-ethylamine,N,N-bis(2-hydroxyethyl)-2-(2-oxopropoxycarbonyl)ethylamine,N,N-bis(2-acetoxyethyl)-2-(2-oxopropoxycarbonyl)ethylamine,N,N-bis(2-hydroxyethyl)-2-(tetrahydrofurfuryloxycarbonyl)ethylamine,N,N-bis(2-acetoxyethyl)-2-(tetrahydrofurfuryloxycarbonyl)ethylamine,N,N-bis(2-hydroxyethyl)-2-[(2-oxotetrahydrofuran-3-yl)oxycarbonyl]ethylamine,N,N-bis(2-acetoxyethyl)-2-[(2-oxotetrahydrofuran-3-yl)oxycarbonyl]ethylamine,N,N-bis(2-hydroxyethyl)-2-(4-hydroxybutoxycarbonyl)ethylamine,N,N-bis(2-formyloxyethyl)-2-(4-formyloxybutoxycarbonyl)ethylamine,N,N-bis(2-formyloxyethyl)-2-(2-formyloxyethoxycarbonyl)ethylamine,N,N-bis(2-methoxyethyl)-2-(methoxycarbonyl)ethylamine,N-(2-hydroxyethyl)-bis[2-(methoxycarbonyl)ethyl]amine,N-(2-acetoxyethyl)-bis[2-(methoxycarbonyl)ethyl]amine,N-(2-hydroxyethyl)-bis[2-(ethoxycarbonyl)ethyl]amine,N-(2-acetoxyethyl)-bis[2-(ethoxycarbonyl)ethyl]amine,N-(3-hydroxy-1-propyl)-bis[2-(methoxycarbonyl)ethyl]amine,N-(3-acetoxy-1-propyl)-bis[2-(methoxycarbonyl)ethyl]amine,N-(2-methoxyethyl)-bis[2-(methoxycarbonyl)ethyl]amine,N-butyl-bis[2-(methoxycarbonyl)ethyl]amine,N-butyl-bis[2-(2-methoxyethoxycarbonyl)ethyl]amine,N-methyl-bis(2-acetoxyethyl)amine, N-ethyl-bis(2-acetoxyethyl)amine,N-methyl-bis(2-pivaloyloxyethyl)amine,N-ethyl-bis[2-(methoxycarbonyloxy)ethyl]amine,N-ethyl-bis[2-(tert-butoxycarbonyloxy)ethyl]amine,tris(methoxycarbonylmethyl)amine, tris(ethoxycarbonylmethyl)amine,N-butyl-bis(methoxycarbonylmethyl)amine,N-hexyl-bis(methoxycarbonylmethyl)amine, andp-(diethylamino)-δ-valerolactone.

Also useful are one or more organic nitrogen-containing compounds havingcyclic structure represented by the following general formula (B)-2.

Herein X is as defined above, and R³⁰⁷ is a straight or branched C₂-C₂₀alkylene group which may contain one or more carbonyl, ether, ester orsulfide groups.

Illustrative examples of the organic nitrogen-containing compoundshaving formula (B)-2 include 1-[2-(methoxymethoxy)ethyl]pyrrolidine,1-[2-(methoxymethoxy)ethyl]piperidine,4-[2-(methoxymethoxy)ethyl]morpholine,1-[2-[(2-methoxyethoxy)methoxy]ethyl]pyrrolidine,1-[2-[(2-methoxyethoxy)methoxy]ethyl]piperidine,4-[2-[(2-methoxyethoxy)methoxy]ethyl]morpholine, 2-(1-pyrrolidinyl)ethylacetate, 2-piperidinoethyl acetate, 2-morpholinoethyl acetate,2-(1-pyrrolidinyl)ethyl formate, 2-piperidinoethyl propionate,2-morpholinoethyl acetoxyacetate, 2-(1-pyrrolidinyl)ethylmethoxyacetate, 4-[2-(methoxycarbonyloxy)ethyl]morpholine,1-[2-(t-butoxycarbonyloxy)ethyl]piperidine,4-[2-(2-methoxyethoxycarbonyloxy)ethyl]morpholine, methyl3-(1-pyrrolidinyl)propionate, methyl 3-piperidinopropionate, methyl3-morpholinopropionate, methyl 3-(thiomorpholino)propionate, methyl2-methyl-3-(1-pyrrolidinyl)propionate, ethyl 3-morpholinopropionate,methoxycarbonylmethyl 3-piperidinopropionate, 2-hydroxyethyl3-(1-pyrrolidinyl)propionate, 2-acetoxyethyl 3-morpholinopropionate,2-oxotetrahydrofuran-3-yl 3-(1-pyrrolidinyl)propionate,tetrahydrofurfuryl 3-morpholinopropionate, glycidyl3-piperidinopropionate, 2-methoxyethyl 3-morpholinopropionate,2-(2-methoxyethoxy)ethyl 3-(1-pyrrolidinyl)propionate, butyl3-morpholinopropionate, cyclohexyl 3-piperidinopropionate,α-(1-pyrrolidinyl)methyl-γ-butyrolactone, β-piperidino-γ-butyrolactone,β-morpholino-δ-valerolactone, methyl 1-pyrrolidinylacetate, methylpiperidinoacetate, methyl morpholinoacetate, methylthiomorpholinoacetate, ethyl 1-pyrrolidinylacetate, 2-methoxyethylmorpholinoacetate, 2-morpholinoethyl 2-methoxyacetate, 2-morpholinoethyl2-(2-methoxyethoxy)acetate, 2-morpholinoethyl2-[2-(2-methoxyethoxy)ethoxy]acetate, 2-morpholinoethyl hexanoate,2-morpholinoethyl octanoate, 2-morpholinoethyl decanoate,2-morpholinoethyl laurate, 2-morpholinoethyl myristate,2-morpholinoethyl palmitate, and 2-morpholinoethyl stearate.

Also, one or more organic nitrogen-containing compounds having cyanogroup represented by the following general formulae (B)-3 to (B)-6 maybe blended.

Herein, X, R³⁰⁷ and n are as defined above, and R³⁰⁸ and R³⁰⁹ are eachindependently a straight or branched C₁-C₄ alkylene group.

Illustrative examples of the organic s nitrogen-containing compoundshaving cyano represented by formulae (B)-3 to (B)-6 include3-(diethylamino)propiononitrile,N,N-bis(2-hydroxyethyl)-3-aminopropiononitrile,N,N-bis(2-acetoxyethyl)-3-aminopropiononitrile,N,N-bis(2-formyloxyethyl)-3-aminopropiononitrile,N,N-bis(2-methoxyethyl)-3-aminopropiononitrile,N,N-bis[2-(methoxymethoxy)ethyl]-3-aminopropiononitrile, methylN-(2-cyanoethyl)-N-(2-methoxyethyl)-3-aminopropionate, methylN-(2-cyanoethyl)-N-(2-hydroxyethyl)-3-aminopropionate, methylN-(2-acetoxyethyl)-N-(2-cyanoethyl)-3-aminopropionate,N-(2-cyanoethyl)-N-ethyl-3-aminopropiononitrile,N-(2-cyanoethyl)-N-(2-hydroxyethyl)-3-aminopropiononitrile,N-(2-acetoxyethyl)-N-(2-cyanoethyl)-3-aminopropiononitrile,N-(2-cyanoethyl)-N-(2-formyloxyethyl)-3-aminopropiononitrile,N-(2-cyanoethyl)-N-(2-methoxyethyl)-3-aminopropiononitrile,N-(2-cyanoethyl)-N-[2-(methoxymethoxy)ethyl]-3-aminopropiononitrile,N-(2-cyanoethyl)-N-(3-hydroxy-1-propyl)-3-aminopropiononitrile,N-(3-acetoxy-1-propyl)-N-(2-cyanoethyl)-3-aminopropiononitrile,N-(2-cyanoethyl)-N-(3-formyloxy-1-propyl)-3-aminopropiononitrile,N-(2-cyanoethyl)-N-tetrahydrofurfuryl-3-aminopropiononitrile,N,N-bis(2-cyanoethyl)-3-aminopropiononitrile, diethylaminoacetonitrile,N,N-bis(2-hydroxyethyl)aminoacetonitrile,N,N-bis(2-acetoxyethyl)aminoacetonitrile.N,N-bis(2-formyloxyethyl)aminoacetonitrile,N,N-bis(2-methoxyethyl)aminoacetonitrile,N,N-bis[2-(methoxymethoxy)ethyl]aminoacetonitrile, methylN-cyanomethyl-N-(2-methoxyethyl)-3-aminopropionate, methylN-cyanomethyl-N-(2-hydroxyethyl)-3-aminopropionate, methylN-(2-acetoxyethyl)-N-cyanomethyl-3-aminopropionate,N-cyanomethyl-N-(2-hydroxyethyl)aminoacetonitrile,N-(2-acetoxyethyl)-N-(cyanomethyl)aminoacetonitrile,N-cyanomethyl-N-(2-formyloxyethyl)aminoacetonitrile,N-cyanomethyl-N-(2-methoxyethyl)aminoacetonitrile,N-cyanomethyl-N-[2-(methoxymethoxy)ethyl)aminoacetonitrile,N-cyanomethyl-N-(3-hydroxy-1-propyl)aminoacetonitrile,N-(3-acetoxy-1-propyl)-N-(cyanomethyl)aminoacetonitrile,N-cyanomethyl-N-(3-formyloxy-1-propyl)aminoacetonitrile,N,N-bis(cyanomethyl)aminoacetonitrile, 1-pyrrolidinepropiononitrile,1-piperidinepropiononitrile, 4-morpholinepropiononitrile,1-pyrrolidineacetonitrile, 1-piperidineacetonitrile,4-morpholineacetonitrile, cyanomethyl 3-diethylaminopropionate,cyanomethyl N,N-bis(2-hydroxyethyl)-3-aminopropionate, cyanomethylN,N-bis(2-acetoxyethyl)-3-aminopropionate, cyanomethylN,N-bis(2-formyloxyethyl)-3-aminopropionate, cyanomethylN,N-bis(2-methoxyethyl)-3-aminopropionate, cyanomethylN,N-bis[2-(methoxymethoxy)ethyl]-3-aminopropionate, 2-cyanoethyl3-diethylaminopropionate, 2-cyanoethylN,N-bis(2-hydroxyethyl)-3-aminopropionate, 2-cyanoethylN,N-bis(2-acetoxyethyl)-3-aminopropionate, 2-cyanoethylN,N-bis(2-formyloxyethyl)-3-aminopropionate, 2-cyanoethylN,N-bis(2-methoxyethyl)-3-aminopropionate, 2-cyanoethylN,N-bis[2-(methoxymethoxy)ethyl]-3-aminopropionate, cyanomethyl1-pyrrolidinepropionate, cyanomethyl 1-piperidinepropionate, cyanomethyl4-morpholinepropionate, 2-cyanoethyl 1-pyrrolidinepropionate,2-cyanoethyl 1-piperidinepropionate, and 2-cyanoethyl4-morpholinepropionate.

Also included are organic nitrogen-containing compounds having animidazole structure and a polar functional group, represented by thegeneral formula (B)-7.

Herein, R³¹⁰ is a straight, branched or cyclic C₂-C₂₀ alkyl groupbearing at least one polar functional group selected from amonghydroxyl, carbonyl, ester, ether, sulfide, carbonate, cyano and acetalgroups; R³¹¹, R³¹² and R³¹³ are each independently a hydrogen atom, astraight, branched or cyclic C₁-C₁₀ alkyl group, aryl group or aralkylgroup.

Also included are organic nitrogen-containing compounds having abenzimidazole structure and a polar functional group, represented by thegeneral formula (B)-8.

Herein, R³¹⁴ is a hydrogen atom, a straight, branched or cyclic C₁-C₁₀alkyl group, aryl group or araikyl group. R³¹⁵ is a polar functionalgroup-bearing, straight, branched or cyclic C₁-C₂₀ alkyl group, and thealkyl group contains as the polar functional group at least one groupselected from among ester, acetal and cyano groups, and may additionallycontain at least one group selected from among hydroxyl, carbonyl,ether, sulfide and carbonate groups.

Further included are heterocyclic nitrogen-containing compounds having apolar functional group, represented by the general formulae (B)-9 and(B)-10.

Herein, A is a nitrogen atom or ≡C—R³²², B is a nitrogen atom or≡C—R³²³, R³¹⁶ is a straight, branched or cyclic C₂-C₂₀ alkyl groupbearing at least one polar functional group selected from amonghydroxyl, carbonyl, ester, ether, sulfide, carbonate, cyano and acetalgroups; R³¹⁷, R³¹⁸, R³¹⁹ and R³²⁰ are each independently a hydrogenatom, a straight, branched or cyclic C₁-C₁₀ alkyl group or aryl group,or a pair of R³¹⁷ and R³¹⁸ or a pair of R³¹⁹ and R³²⁰ may bond togetherto form a benzene, naphthalene or pyridine ring with the carbon atoms towhich they are attached; R³²¹ is a hydrogen atom, a straight, branchedor cyclic C₁-C₁₀ alkyl group or aryl group; R³²² and R³²³ each are ahydrogen atom, a straight, branched or cyclic C₁-C₁₀ alkyl group or arylgroup, or a pair of R³²¹ and R³²³, taken together, may form a benzene ornaphthalene ring.

Also included are organic nitrogen-containing compounds of aromaticcarboxylic ester structure having the general formulae (B)-11 to (B)-14.

Herein R³²⁴ is a C₆-C₂₀ aryl group or C₄-C₂₀ hetero-aromatic group, inwhich some or all of hydrogen atoms may be replaced by halogen atoms,straight, branched or cyclic C₁-C₂₀ alkyl groups, C₆-C₂₀ aryl groups,C₇-C₂₀ aralkyl qroups, C₁-C₁₀ alkoxy groups, C₁-C₁₀ acyloxy groups orC₁-C₁₀ alkylthio groups. R³²⁵ is CO₂R³²⁶, OR³²⁷ or cyano group. R³²⁶ isa C₁-C₁₀ alkyl group, in which some methylene groups may be replaced byoxygen atoms. R³²⁷ is a C₁-C₁₀ alkyl or acyl group, in which somemethylene groups may be replaced by oxygen atoms. R³²⁸ is a single bond,methylene, ethylene, sulfur atom or —O(CH₂CH₂O)_(n)— group wherein n is0, 1, 2, 3 or 4. R³²⁹ is hydrogen, methyl, ethyl or phenyl. X is anitrogen atom or CR³³⁰. Y is a nitrogen atom or CR³³¹. Z is a nitrogenatom or CR³³². R³³⁰, R³³¹ and R³³² are each independently hydrogen,methyl or phenyl. Alternatively, a pair of R³³⁰ and R³³¹ or a pair ofR³³¹ and R³³² may bond together to form a C₆-C₂₀ aromatic ring or C₂-C₂₀hetero-aromatic ring with the carbon atoms to which they are attached.

Further included are organic nitrogen-containing compounds of7-oxanorbornane-2-carboxylic ester structure having the general formula(B)-15.

Herein R³³³ is hydrogen or a straight, branched or cyclic C₁-C₁₀ alkylgroup. R³³⁴ and R³³⁵ are each independently a C₁-C₂₀ alkyl group, C₆-C₂₀aryl group or C₇-C₂₀ aralkyl group, which may contain one or more polarfunctional groups selected from among ether, carbonyl, ester, alcohol,sulfide, nitrile, amine, imine, and amide and in which some hydrogenatoms may be replaced by halogen atoms. R³³⁴ and R³³⁵ may bond togetherto form a heterocyclic or hetero-aromatic ring of 2 to 20 carbon atomswith the nitrogen atom to which they are attached.

The organic nitrogen-containing compounds may be used alone or inadmixture of two or more. The organic nitrogen-containing compound ispreferably formulated in an amount of 0.001 to 4 parts, and especially0.01 to 2 parts by weight, per 100 parts by weight of the base polymer.Less than 0.001 part of the nitrogen-containing compound achieves no orlittle addition effect whereas more than 4 parts may result in too low asensitivity.

Other Components

The resist composition of the invention may include optionalingredients, for example, a surfactant which is commonly used forimproving the coating characteristics. Optional ingredients may be addedin conventional amounts so long as this does not compromise the objectsof the invention.

Nonionic surfactants are preferred, examples of which includeperfluoroalkylpolyoxyethylene ethanols, fluorinated alkyl esters,perfluoroalkylamine oxides, perfluoroalkyl EO-addition products, andfluorinated organosiloxane compounds. Useful surfactants arecommercially available under the trade names Fluorad FC-430, FC-431,FC-4430 and FC-4432 from Sumitomo 3M, Ltd., Surflon S-141, S-145, KH-10,KH-20, KH-30 and KH-40 from Asahi Glass Co., Ltd., Unidyne DS-401,DS-403 and DS-451 from Daikin Industry Co., Ltd., Megaface F-8151 fromDai-Nippon Ink & Chemicals, Inc., and X-70-092 and X-70-093 fromShin-Etsu Chemical Co., Ltd. Preferred surfactants are Fluorad FC-430and FC-4430 from Sumitomo 3M, Ltd., KH-20 and KH-30 from Asahi GlassCo., Ltd., and X-70-093 from Shin-Etsu Chemical Co., Ltd.

Optionally, there may be added to the resist composition of theinvention a polymer which will be locally distributed at the top of acoating and functions to adjust a hydrophilic/hydrophobic balance at thesurface, to enhance water repellency, or to prevent low-molecular-weightcomponents from flowing into or out of the coating when the coatingcomes in contact with water or similar liquids, that is, a polymericsurfactant which is insoluble in water and soluble in alkalinedeveloper. The functional polymer may be added in customary amounts aslong as it does not compromise the objects of the invention. Thepreferred amount of the functional polymer added is 0 to 10 parts byweight per 100 parts by weight of the base polymer, and when added, atleast 0.1 part by weight.

Preferred examples of the functional polymer which will be localized atthe coating top include polymers and copolymers comprising fluorinatedunits of one or more types, and copolymers comprising fluorinated unitsand other units. Illustrative examples of suitable fluorinated units andother units are shown below, but not limited thereto.

The functional polymer which will be localized at the coating top shouldpreferably have a weight average molecular weight of 1,000 to 50,000,more preferably 2,000 to 20,000, as measured by GPC versus polystyrenestandards. Outside the range, the polymer may have insufficientsurface-modifying effect or cause development defects.

To the resist composition of the invention, other components such asdissolution regulators, carboxylic acid compounds and acetylene alcoholderivatives may be added if necessary. Optional components may be addedin conventional amounts so long as this does not compromise the objectsof the invention.

The dissolution regulator which can be added to the resist compositionis a compound having on the molecule at least two phenolic hydroxylgroups, in which an average of from 0 to 100 mol % of all the hydrogenatoms on the phenolic hydroxyl groups are replaced by acid labile groupsor a compound having on the molecule at least one carboxyl group, inwhich an average of 50 to 100 mol % of all the hydrogen atoms on thecarboxyl groups are replaced by acid labile groups, both the compoundshaving a weight average molecular weight within a range of 100 to 1,000,and preferably 150 to 800.

The degree of substitution of the hydrogen atoms on the phenolichydroxyl groups with acid labile groups is on average at least 0 mol %,and preferably at least 30 mol %, of all the phenolic hydroxyl groups.The upper limit is 100 mol %, and preferably 80 mol %. The degree ofsubstitution of the hydrogen atoms on the carboxyl groups with acidlabile groups is on average at least 50 mol %, and preferably at least70 mol %, of all the carboxyl groups, with the upper limit being 100 mol%.

Preferable examples of such compounds having two or more phenolichydroxyl groups or compounds having a carboxyl group include those offormulas (D1) to (D14) below.

In these formulas, R²⁰¹ and R²⁰² are each hydrogen or a straight orbranched C₁-C₈ alkyl or alkenyl group, for example, hydrogen, methyl,ethyl, butyl, propyl, ethynyl and cyclohexyl.

R²⁰³ is hydrogen, a straight or branched C₁-C₈ alkyl or alkenyl group,or —(R²⁰⁷)_(h)—COOH wherein R²⁰⁷ is a straight or branched C₁-C₁₀alkylene, for example, those exemplified for R²⁰¹ and R²⁰² and —COOH and—CH₂COOH.

R²⁰⁴ is —(CH₂)₁— wherein i=2 to 10, C₆-C₁₀ arylene, carbonyl, sulfonyl,an oxygen atom, or a sulfur atom, for example, ethylene, phenylene,carbonyl, sulfonyl, oxygen atom or sulfur atom.

R²⁰⁵ is a C₁-C₁₀ alkylene, a C₆-C₁₀ arylene, carbonyl, sulfonyl, anoxygen atom, or a sulfur atom, for example, methylene and thoseexemplified for R²⁰⁴.

R²⁰⁶ is hydrogen, a straight or branched C₁-C₈ alkyl or alkenyl, or aphenyl or naphthyl group in which at least one hydrogen atom issubstituted by a hydroxyl group, for example, hydrogen, methyl, ethyl,butyl, propyl, ethynyl, cyclohexyl, hydroxyl-substituted phenyl, andhydroxyl-substituted naphthyl.

R²⁰⁸ is hydrogen or hydroxyl.

The letter j is an integer from 0 to 5; u and h are each 0 or 1; s, t,s′, t′, s″, and t″ are each numbers which satisfy s+t=8, s′+t′=5, ands″+t″=4, and are such that each phenyl structure has at least onehydroxyl group; and α is a number such that the compounds of formula(D8) or (D9) have a weight average molecular weight of from 100 to1,000.

Exemplary acid labile groups on the dissolution regulator include avariety of such groups, typically groups of the general formulae (L1) to(L4), tertiary C₄-C₂₀ alkyl groups, trialkylsilyl groups in which eachof the alkyls has 1 to 6 carbon atoms, and C₄-C₂₀ oxoalkyl groups.Examples of the respective groups are as previously described.

The dissolution regulator may be formulated in an amount of 0 to 50parts, preferably 0 to 40 parts, and more preferably 0 to 30 parts byweight, per 100 parts by weight of the base polymer, and may be usedsingly or as a mixture of two or more thereof. The use of more than 50parts of the dissolution regulator may lead to slimming of the patternedfilm, and thus a decline in resolution.

The dissolution regulator can be synthesized by introducing acid labilegroups into a compound having phenolic hydroxyl or carboxyl groups inaccordance with an organic chemical formulation.

In the resist composition, a carboxylic acid compound may be blended.The carboxylic acid compound used herein may be one or more compoundsselected from Groups I and II below, but is not limited thereto.Including this compound improves the PED stability of the resist andameliorates edge roughness on nitride film substrates.

Group I:

Compounds of general formulas (A1) to (A10) below in which some or allof the hydrogen atoms on the phenolic hydroxyl groups are replaced by—R⁴⁰¹—COOH (wherein R⁴⁰¹ is a straight or branched C₁-C₁₀ alkylenegroup), and in which the molar ratio C/(C+D) of phenolic hydroxyl groups(C) to ≡C—COOH groups (D) in the molecule is from 0.1 to 1.0.

Group II:

Compounds of general formulas (A11) to (A15) below.

In these formulas, R⁴⁰² and R⁴⁰³ are each hydrogen or a straight orbranched C₁-C₈ alkyl or alkenyl. R⁴⁰⁴ is hydrogen, a straight orbranched C₁-C₈ alkyl or alkenyl, or a —(R⁴⁰⁹)_(h1)—COOR′ group whereinR′ is hydrogen or —R⁴⁰⁹—COOH.

R⁴⁰⁵ is —(CH₂)₁— (wherein i is 2 to 10), a C₆-C₁₀ arylene, carbonyl,sulfonyl, an oxygen atom, or a sulfur atom. R⁴⁰⁶ is a C₁-C₁₀ alkylene, aC₆-C₁₀ arylene, carbonyl, sulfonyl, an oxygen atom, or a sulfur atom.R⁴⁰⁷ is hydrogen, a straight or branched C₁-C₈ alkyl or alkenyl, or ahydroxyl-substituted phenyl or naphthyl. R⁴⁰⁸ is hydrogen or methyl.R⁴⁰⁹ is a straight or branched C₁-C₁₀ alkylene. R⁴¹⁰ is hydrogen, astraight or branched C₁-C₈ alkyl or alkenyl, or a —R⁴¹¹—COOH groupwherein R⁴¹¹ is a straight or branched C₁-C₁₀ alkylene. R⁴¹² is hydrogenor hydroxyl.

The letter j is a number from 0 to 3; s1, t1, s2, t2, s3, t3, s4, and t4are each numbers which satisfy s1+t1=8, s2+t2=5, s3+t3=4, and s4+t4=6,and are such that each phenyl structure has at least one hydroxyl group;s5 and t5 are numbers which satisfy s5≧0, t5≧0, and s5+t5=5; u1 is anumber from 1 to 4; h1 is a number from 0 to 4; κ is a number such thatthe compound of formula (A6) may have a weight average molecular weightof 1,000 to 5,000; and λ is a number such that the compound of formula(A7) may have a weight average molecular weight of 1,000 to 10,000.

Illustrative, non-limiting examples of the compound having a carboxylgroup include compounds of the general formulas AI-1 to AI-14 and AII-1to AII-10 below.

In the above formulas, R″ is hydrogen or a —CH₂COOH group such that the—CH₂COOH group accounts for 10 to 100 mol % of R″ in each compound, κand λ are as defined above.

The compound having a —C—COOH group may be used singly or ascombinations of two or more thereof. The compound having a ≡C—COOH groupis added in an amount ranging from 0 to 5 parts, preferably 0.1 to 5parts, more preferably 0.1 to 3 parts, further preferably 0.1 to 2 partsby weight, per 100 parts by weight of the base polymer. More than 5parts of the compound can reduce the resolution of the resistcomposition.

Preferred examples of the acetylene alcohol derivative which can beadded to the resist composition include those having the general formula(S1) or (S2) below.

In the formulas, R⁵⁰¹, R⁵⁰², R⁵⁰³, R⁵⁰⁴, and R⁵⁰⁵ are each hydrogen or astraight, branched or cyclic C₁-C₈ alkyl; and X and Y are each 0 or apositive number, satisfying 0≦X≦30, 0≦Y≦30, and 0≦X+Y≦40.

Preferable examples of the acetylene alcohol derivative include Surfynol61, Surfynol 82, Surfynol 104, Surfynol 104E, Surfynol 104H, Surfynol104A, Surfynol TG, Surfynol PC, Surfynol 440, Surfynol 465, and Surfynol485 from Air Products and Chemicals Inc., and Surfynol E1004 fromNisshin Chemical Industries Ltd.

The acetylene alcohol derivative is preferably added in an amount of 0to 2 parts, more preferably 0.01 to 2 parts, and even more preferably0.02 to 1 part by weight per 100 parts by weight of the base polymer inthe resist composition. More than 2 parts by weight may result in aresist having a low resolution.

Process

Pattern formation using the resist composition of the invention may beperformed by well-known lithography processes. The process generallyinvolves coating, heat treatment (or prebaking), exposure, heattreatment (post-exposure baking, PEB), and development. If necessary,any other steps may be added.

For pattern formation, the resist composition is first applied onto asubstrate (on which an integrated circuit is to be formed, e.g., Si,SiO₂, SiN, SiON, TiN, WSi, BPSG, SOG, organic antireflective coating,Cr, CrO, CrON, MoSi, etc.) by a suitable coating technique such as spincoating, roll coating, flow coating, dip coating, spray coating ordoctor coating. The coating is prebaked on a hot plate at a temperatureof 60 to 150° C. for about 1 to 10 minutes, preferably 80 to 140° C. for1 to 5 minutes. The resulting resist film is generally 0.01 to 2.0 μmthick.

A relationship of a reduced thickness of resist film to an etchselectivity ratio between resist film and processable substrate imposesseverer limits on the process. Under consideration is the tri-layerprocess in which a resist layer, a silicon-containing intermediatelayer, an undercoat layer having a high carbon density and high etchresistance, and a processable substrate are laminated in sequence fromtop to bottom. On etching with oxygen gas, hydrogen gas, ammonia gas orthe like, a high etch selectivity ratio is available between thesilicon-containing intermediate layer and the undercoat layer, whichallows for thickness reduction of the silicon-containing intermediatelayer. A relatively high etch selectivity ratio is also availablebetween the monolayer resist and the silicon-containing intermediatelayer, which allows for thickness reduction of the monolayer resist. Themethod for forming the undercoat layer in this case includes a coatingand baking method and a CVD method. In the case of coating, novolacresins and resins obtained by polymerization of fused ring-containingolefins are used. In the CVD film formation, gases such as butane,ethane, propane, ethylene and acetylene are used. For thesilicon-containing intermediate layer, either a coating method or a CVDmethod may be employed. The coating method uses silsesquioxane,polyhedral oligomeric silsesquioxane (POSS) and the like while the CVDmethod uses silane gases as the reactant. The silicon-containingintermediate layer may have an antireflection function with a lightabsorbing ability and have photo-absorptive groups like phenyl groups,or it may be a SiON film. An organic film may be formed between thesilicon-containing intermediate layer and the photoresist, and theorganic film in this case may be an organic antireflective coating.After the photoresist film is formed, deionized water rinsing (orpost-soaking) may be carried out for extracting the acid generator andthe like from the film surface or washing away particles, or aprotective film may be coated.

With a mask having a desired pattern placed above the resist film, theresist film is then exposed to actinic radiation such as UV, deep-UV,electron beams, x-rays, excimer laser light, γ-rays and synchrotronradiation. Alternatively, pattern formation may be performed by directwriting imagewise with an electron beam without a mask. The exposuredose is preferably about 1 to 200 mJ/cm², more preferably about 10 to100 mJ/cm². The film is further baked on a hot plate at 60 to 150° C.for 1 to 5 minutes, preferably 80 to 120° C. for 1 to 3 minutes(post-exposure baking=PEB). Thereafter the resist film is developed witha developer in the form of an aqueous base solution, for example, 0.1 to5 wt %, preferably 2 to 3 wt % aqueous solution of tetramethylammoniumhydroxide (TMAH) for 0.1 to 3 minutes, preferably 0.5 to 2 minutes byconventional techniques such as dip, puddle or spray techniques. In thisway, a desired resist pattern is formed on the substrate. It isappreciated that the resist composition of the invention is suited formicro-patterning using such high-energy radiation as deep UV with awavelength of 254 to 193 nm, vacuum UV with a wavelength of 157 nm,electron beams, soft x-rays, x-rays, excimer laser light, γ-rays andsynchrotron radiation, and best suited for micro-patterning usinghigh-energy radiation in the wavelength range of 180 to 200 nm.

Immersion lithography can be applied to the resist composition of theinvention. The ArF immersion lithography uses a liquid having arefractive index of at least 1 and least absorptive to exposureradiation, such as deionized water or alkanes as the immersion solvent.The immersion lithography involves prebaking a resist film and exposingthe resist film to light through a projection lens, with deionized wateror similar liquid interposed between the resist film and the projectionlens. Since this allows projection lenses to be designed to a numericalaperture (NA) of 1.0 or higher, formation of finer patterns is possible.The immersion lithography is important for the ArF lithography tosurvive to the 45-nm node, with a further development thereof beingaccelerated. In the case of immersion lithography, deionized waterrinsing (or post-soaking) may be carried out after exposure for removingwater droplets left on the resist film, or a protective coating may beapplied onto the resist film after pre-baking for preventing anydissolution from the resist and improving water slip on the filmsurface. The resist protective coating used in the immersion lithographyis preferably formed from a solution of a polymer having1,1,1,3,3,3-hexafluoro-2-propanol residue which is insoluble in waterand soluble in an alkaline developer liquid, in a solvent selected fromalcohols of at least 4 carbon atoms, ethers of 8 to 12 carbon atoms, andmixtures thereof.

Also useful is a solution of a surfactant which is insoluble in waterand soluble in an alkaline developer liquid, in a solvent selected fromalcohols of at least 4 carbon atoms, ethers of 8 to 12 carbon atoms, andmixtures thereof.

In the process for pattern formation, after formation of a photoresistfilm, deionized water rinsing (or post-soaking) may be carried out forthe purposes of extracting the acid generator from the film surface orwashing away particles, or rinsing (or post-soaking) may be carried outfor the purposes of removing water remaining on the resist film afterexposure.

The technique enabling the ArF lithography to survive to the 32-nm nodeis a double patterning process. The double patterning process includes atrench process of processing an underlay to a 1:3 trench pattern by afirst step of exposure and etching, shifting the position, and forming a1:3 trench pattern by a second step of exposure, for forming a 1:1pattern; and a line process of processing a first underlay to a 1:3isolated left pattern by a first step of exposure and etching, shiftingthe position, processing a second underlay formed below the firstunderlay by a second step of exposure through the 1:3 isolated leftpattern, for forming a half-pitch 1:1 pattern.

EXAMPLE

Examples of the invention are given below by way of illustration and notby way of limitation. Mw is weight average molecular weight.

Synthesis of Photoacid Generator Reference Example Synthesis of sodium2-(1-adamantanecarbonyloxy)-1,1-difluoroethanesulfonate [Anion-1]

In tetrahydrofuran, 1-adamantanecarbonyl chloride and2-bromo-2,2-difluoroethanol were mixed and ice cooled. Triethylamine wasadded to the mixture. By standard separation operation and solventdistillation, 2-bromo-2,2-difluoroethyl 1-adamantanecarboxylate wasobtained. This compound was converted into a sodium sulfinate withsodium dithionite and then oxidized with hydrogen peroxide, yielding thetarget compound, sodium2-(1-adamantanecarbonyloxy)-1,1-difluoroethanesulfonate.

Synthesis of carboxylic ester is well known, and synthesis of sulfinicacid and sulfonic acid from alkyl halide is also well known. The latteris described, for example, in JP-A 2004-2252.

Synthesis of sodium 2-(pivaloyloxy)-1,1-difluoroethanesulfonate[Anion-2]

The target compound was obtained as was Anion-1 except that pivalic acidchloride was used in lieu of 1-adamantanecarbonyl chloride.

Synthesis of triphenylsulfonium2-(pivaloyloxy)-1,1-difluoroethanesulfonate [PAG-1]

In 700 g of dichloromethane and 400 g of water were dissolved 159 g(0.37 mole) of sodium 2-(pivaloyloxy)-1,1-difluoroethanesulfonate(purity 63%) and 132 g (0.34 mole) of triphenylsulfonium iodide. Theorganic layer was separated, washed three times with 200 g of water, andconcentrated. Diethyl ether was added to the residue forrecrystallization, obtaining the target compound as white crystals. 164g (yield 95%).

Synthesis of triphenylsulfonium2-(1-adamantanecarbonyl-oxy)-1,1-difluoroethanesulfonate [PAG-2]

In 100 g of dichloromethane were dissolved 10 g (0.02 mole) of sodium2-(1-adamantanecarbonyloxy)-1,1-difluoroethanesulfonate (purity 70%) and50 g (0.02 mole) of a triphenylsulfonium chloride aqueous solution. Theorganic layer was separated, washed three times with 20 g of water, andconcentrated. Diethyl ether was added to the residue forrecrystallization, obtaining the target compound as white crystals. 10 g(yield 85%).

Synthesis of 4-tert-butylphenyldiphenylsulfonium2-(pivaloyloxy)-1,1-difluoroethanesulfonate [PAG-3]

In 150 g of dichloromethane were dissolved 20 g (0.052 mole) of sodium2-(pivaloyloxy)-1,1-difluoroethanesulfonate (purity 70%) and 217 g(0.052 mole) of a 4-tert-butylphenyldiphenylsulfonium bromide aqueoussolution. The organic layer was separated, washed three times with 50 gof water, and concentrated. Diethyl ether was added to the residue forrecrystallization, obtaining the target compound as white crystals. 26 g(yield 79%).

Synthesis of 4-tert-butylphenyldiphenylsulfonium2-(1-adamantanecarbonyloxy)-1,1-difluoroethanesulfonate [PAG-4]

In 100 g of dichloromethane were dissolved 10 g (0.02 mole) of sodium2-(1-adamantanecarbonyloxy)-1,1-difluoroethanesulfonate (purity 70%) and80 g (0.02 mole) of a 4-tert-butylphenyldiphenylsulfonium bromideaqueous solution. The organic layer was separated, washed three timeswith 20 g of water, and concentrated. Diethyl ether was added to theresidue for recrystallization, obtaining the target compound as whitecrystals. 11 g (yield 86%).

Synthesis of triphenylsulfonium 1,1-difluoro-2-hydroxyethanesulfonate(Intermediate)

Triphenylsulfonium 2-(pivaloyloxy)-1,1-difluoroethanesulfonate, 243.5 g(0.48 mole), was dissolved in 760 g of methanol and ice cooled. Anaqueous solution of 40 g sodium hydroxide in 120 g water was addeddropwise to the solution at a temperature below 5° C. It was aged atroom temperature for 8 hours. At a temperature below 10° C., dilutehydrochloric acid (99.8 g of 12N hydrochloric acid in 200 g of water)was added to quench the reaction. The methanol was distilled off invacuum, after which 1,000 g of dichloromethane was added to the residue.The organic layer was washed with 30 g of a saturated sodium chloridesolution three times. The organic layer was concentrated, after which 1L of diisopropyl ether was added to the residue for crystallization. Thecrystals were filtered and dried, obtaining the target compound. 187 g(purity 78%, net yield 78%).

Synthesis of triphenylsulfonium2-(4-adamantanone-1-carbonyloxy)-1,1-difluoroethanesulfonate [PAG-5]

4-adamantanone-1-carboxylic acid was synthesized through reaction of5-hydroxy-2-adamantanone with sulfuric acid and formic acid and thenconverted into a corresponding carboxylic acid chloride, using oxalylchloride.

In 20 g of acetonitrile, 5.4 g (0.01 mole) of the intermediate,triphenylsulfonium 1,1-difluoro-2-hydroxyethanesulfonate (purity 78%),1.0 g (0.01 mole) of triethylamine and 0.24 g (0.002 mole) ofN,N-dimethylaminopyridine were dissolved and ice cooled. 2.6 g (0.012mole) of 4-adamantanone-1-carbonyl chloride, prepared above, was addeddropwise to the solution at a temperature below 5° C. It was stirred atroom temperature for 1 hour. Dilute hydrochloric acid (1 g of 12Nhydrochloric acid in 10 g of water) was added to the solution. Theacetonitrile was distilled off in vacuum, after which 50 g ofdichloromethane, 50 g of methyl isobutyl ketone, and 20 g of water wereadded to the residue. The organic layer was separated and washed with 20g of water. The solvent was distilled off in vacuum. Ether was added tothe residue for crystallization. The crystals were filtered and dried,obtaining the target compound. 4.8 g (yield 80%). On ¹H-NMR analysis,methyl isobutyl ketone and ether were observed as a trace amount ofresidual solvent.

These compounds PAG-1 to PAG-5 have the structural formulae shown below.

FIGS. 1 to 10 are nuclear magnetic resonance spectra, ¹H-NMR and ¹⁹F-NMRof PAG-1 to PAG-5.

Preparation of Resist Composition

Resist compositions were prepared by mixing and dissolving a polymer,acid generator, and basic compound in a solvent according to theformulation shown in Table 1. They were filtered through a Teflon®filter having a pore size of 0.2 μm, giving resist solutions. In allruns, the solvent contained 0.005 wt % of surfactant KH-20 (Asahi GlassCo., Ltd.).

TABLE 1 Resist Resin Acid generator Base Solvent 1 Solvent 2 R-01P-01(80) PAG-5(9.3) Base-1(1.4) PGMEA(1,120) CyHO(480) R-02 P-02(80)PAG-5(9.3) Base-1(1.4) PGMEA(1,120) CyHO(480) R-03 P-03(80) PAG-5(9.3)Base-1(1.4) PGMEA(1,120) CyHO(480) R-04 P-04(80) PAG-5(9.3) Base-1(1.4)PGMEA(1,120) CyHO(480) R-05 P-05(80) PAG-5(9.3) Base-1(1.4) PGMEA(1,120)CyHO(480) R-06 P-06(80) PAG-5(9.3) Base-1(1.4) PGMEA(1,120) CyHO(480)R-07 P-07(80) PAG-5(9.3) Base-1(1.4) PGMEA(1,120) CyHO(480) R-08P-08(80) PAG-5(9.3) Base-1(1.4) PGMEA(1,120) CyHO(480) R-09 P-09(80)PAG-5(9.3) Base-1(1.4) PGMEA(1,120) CyHO(480) R-10 P-10(80) PAG-5(9.3)Base-1(1.4) PGMEA(1,120) CyHO(480) R-11 P-11(80) PAG-5(9.3) Base-1(1.4)PGMEA(1,120) CyHO(480) R-12 P-12(80) PAG-5(9.3) Base-1(1.4) PGMEA(1,120)CyHO(480) R-13 P-13(80) PAG-5(9.3) Base-1(1.4) PGMEA(1,120) CyHO(480)R-14 P-14(80) PAG-5(9.3) Base-1(1.4) PGMEA(1,120) CyHO(480) R-15P-15(80) PAG-5(9.3) Base-1(1.4) PGMEA(1,120) CyHO(480) R-16 P-01(80)PAG-4(9.9) Base-1(1.4) PGMEA(1,120) CyHO(480) R-17 P-01(80) PAG-1(7.9)Base-1(1.4) PGMEA(1,120) CyHO(480) R-18 P-01(80) PAG-2(9.1) Base-1(1.4)PGMEA(1,120) CyHO(480) R-19 P-01(80) PAG-2(9.1) Base-1(1.4) PGMEA(1,120)CyHO(480) PAG-4(4.9) R-20 P-01(80) PAG-2(9.1) Base-1(1.4) PGMEA(1,120)CyHO(480) PAG-7(5.0) R-21 P-05(80) PAG-4(9.9) Base-1(1.4) PGMEA(1,120)CyHO(480) R-22 P-05(80) PAG-2(9.1) Base-1(1.4) PGMEA(1,120) CyHO(480)R-23 P-05(80) PAG-1(7.9) Base-1(1.4) PGMEA(1,120) CyHO(480) R-24P-07(80) PAG-4(9.9) Base-1(1.4) PGMEA(1,120) CyHO(480) R-25 P-07(80)PAG-1(7.8) Base-1(1.4) PGMEA(1,120) CyHO(480) R-26 P-07(80) PAG-2(9.1)Base-1(1.4) PGMEA(1,120) CyHO(480)

Comparative resist compositions were similarly prepared according to theformulation shown in Table 2.

TABLE 2 Resist Resin Acid generator Base Solvent 1 Solvent 2 R-27P-16(80) PAG-2(9.1) Base-1(1.4) PGMEA(1,120) CyHO(480) R-28 P-17(80)PAG-2(9.1) Base-1(1.4) PGMEA(1,120) CyHO(480) R-29 P-18(80) PAG-2(9.1)Base-1(1.4) PGMEA(1,120) CyHO(480) R-30 P-01(80) PAG-6(8.7) Base-1(1.4)PGMEA(1,120) CyHO(480) R-31 P-05(80) PAG-6(8.7) Base-1(1.4) PGMEA(1,120)CyHO(480) R-32 P-07(80) PAG-6(8.7) Base-1(1.4) PGMEA(1,120) CyHO(480)R-33 P-01(80) PAG-7(9.3) Base-1(1.4) PGMEA(1,120) CyHO(480) R-34P-05(80) PAG-7(9.3) Base-1(1.4) PGMEA(1,120) CyHO(480) R-35 P-07(80)PAG-7(9.3) Base-1(1.4) PGMEA(1,120) CyHO(480)

In Tables 1 and 2, numerical values in parentheses are in parts byweight. The abbreviations for the basic compounds and solvents have thefollowing meaning.

-   Base-1: tri (2-methoxymethoxyethyl)amine-   PGMEA: 1-methoxy-2-propyl acetate-   CyHO: cyclohexanone

Polymers designated P-01 to P-15 are as shown in Tables 3 to 8.

TABLE 3 Unit 1 Unit 2 Unit 3 Unit 4 Resin (ratio) (ratio) (ratio)(ratio) Mw P-01 A-1M(0.30) B-1M(0.15) C-1M(0.30) D-1M(0.25) 7,100 P-02A-2M(0.30) B-1M(0.15) C-1M(0.30) D-1M(0.25) 6,800 P-03 A-3M(0.30)B-1M(0.15) C-1M(0.30) D-1M(0.25) 6,500 P-04 A-4M(0.30) B-1M(0.15)C-1M(0.30) D-1M(0.25) 7,000 P-05 A-5M(0.30) B-1M(0.15) C-1M(0.30)D-1M(0.25) 7,200 P-06 A-1M(0.30) B-1M(0.15) C-2M(0.30) D-1M(0.25) 7,300P-07 A-2M(0.30) B-1M(0.15) C-2M(0.30) D-1M(0.25) 6,800 P-08 A-1M(0.30)B-1M(0.15) C-3M(0.30) D-1M(0.25) 7,300 P-09 A-2M(0.30) B-1M(0.15)C-3M(0.30) D-1M(0.25) 6,900 P-10 A-1M(0.30) B-1M(0.15) C-1M(0.30)D-3M(0.25) 6,900 P-11 A-1M(0.30) B-1M(0.15) C-2M(0.30) D-3M(0.25) 6,900P-12 A-2M(0.30) B-1M(0.15) C-1M(0.30) D-3M(0.25) 6,600 P-13 A-2M(0.30)B-1M(0.15) C-2M(0.30) D-3M(0.25) 6,500 P-14 A-1M(0.30) B-2M(0.15)C-1M(0.30) D-1M(0.25) 7,000 P-15 A-1M(0.30) B-1A(0.15) C-1M(0.30)D-1M(0.25) 6,700 P-16 A-2M(0.30) B-1M(0.15) C-2M(0.55) 6,700 P-17A-2M(0.30) B-1M(0.15) E-1M(0.55) 6,900 P-18 A-2M(0.30) B-1M(0.15)E-2M(0.55) 6,700The “ratio” is a molar ratio of a certain unit incorporated in thepolymer.

TABLE 4 A-1M (R = CH₃) A-2M (R = CH₃) A-3M (R = CH₃) A-4M (R = CH₃) A-5M(R = CH₃) A-1A (R = H) A-2A (R = H) A-3A (R = H) A-4A (R = H) A-5A (R =H)

TABLE 5 B-1M (R = CH₃) B-2M (R = CH₃) B-1A (R = H) B-2A (R = H)

TABLE 6 C-1M (R = CH₃) C-2M (R = CH₃) C-3M (R = CH₃) C-1A (R = H) C-2A(R = H) C-3A (R = H)

TABLE 7 D-1M (R = CH₃) D-2M (R = CH₃) D-3M (R = CH₃) D-1D (R = H) D-2A(R = H) D-3A (R = H)

TABLE 8 E-1M (R = CH₃) E-2M (R = CH₃) E-1A (R = H) E-2A (R = H)

The acid generators designated by abbreviation PAG in Tables 1 and 2 arethe sulfonium salt compounds shown in Table 9.

TABLE 9 [PAG-1]

[PAG-2]

[PAG-4]

[PAG-5]

[PAG-6]

[PAG-7]

Evaluation of Resolution Examples 1 to 26 & Comparative Examples 1 to 9

Each of inventive resist compositions R-01 to 26 and comparative resistcompositions R-27 to 35, prepared above, was spin coated on a siliconwafer having an antireflective coating (ARC-29A, by Nissan Chemical Co.,Ltd.) of 78 nm thick and baked at 100° C. for 60 seconds, forming aresist film of 120 nm thick. The resist film was exposed by means of anArF excimer laser stepper (Nikon Corp., NA 0.85), post-exposure baked(PEB) for 60 seconds, and puddle developed with a 2.38 wt % aqueoussolution of tetramethylammonium hydroxide (TMAH) for 30 seconds. In thisway, 1:1 line-and-space patterns and 1:10 isolated line patterns wereformed. The PEB step used an optimum temperature for a particular resistcomposition.

The pattern-bearing wafers were observed under a top-down scanningelectron microscope (TDSEM). The optimum exposure was an exposure dose(mJ/cm²) which provided a 1:1 resolution at the top and bottom of a80-nm 1:1 line-and-space pattern. The maximum resolution of the resistwas defined as the minimum line width (on-mask size, in increments of 5nm) of a 1:1 line-and-space pattern that was found resolved andseparated at the optimum exposure, with smaller values indicating betterresolution. The 1:10 isolated line pattern at the optimum exposure wasalso observed for determining an actual on-wafer size of the isolatedline pattern with an on-mask size of 140 nm, which was reported as maskfidelity (on-wafer size, a larger size being better). The pattern wasobserved for roughness, and line edge roughness (LER) was evaluated inthree ratings of Good, Fair, and Poor.

Tables 10 and 11 tabulate the test results (maximum resolution, maskfidelity, and LER) of the inventive and comparative resist compositions,respectively.

TABLE 10 Exam- Optimum Maximum Mask ple Resist PEB temp. exposureresolution fidelity LER 1 R-01 95° C. 26.0 mJ/cm² 65 nm 82 nm Good 2R-02 95° C. 29.0 mJ/cm² 65 nm 83 nm Good 3 R-03 95° C. 28.0 mJ/cm² 65 nm83 nm Good 4 R-04 95° C. 29.0 mJ/cm² 65 nm 84 nm Good 5 R-05 105° C. 30.0 mJ/cm² 70 nm 77 nm Good 6 R-06 95° C. 26.0 mJ/cm² 65 nm 79 nm Good7 R-07 95° C. 27.0 mJ/cm² 65 nm 80 nm Good 8 R-08 95° C. 26.0 mJ/cm² 70nm 78 nm Good 9 R-09 95° C. 28.0 mJ/cm² 65 nm 80 nm Good 10 R-10 95° C.26.0 mJ/cm² 65 nm 77 nm Good 11 R-11 95° C. 27.0 mJ/cm² 65 nm 79 nm Good12 R-12 95° C. 25.0 mJ/cm² 65 nm 77 nm Good 13 R-13 95° C. 26.0 mJ/cm²65 nm 78 nm Good 14 R-14 95° C. 28.0 mJ/cm² 65 nm 80 nm Good 15 R-15 95°C. 29.0 mJ/cm² 65 nm 81 nm Good 16 R-16 95° C. 27.0 mJ/cm² 65 nm 79 nmGood 17 R-17 95° C. 27.0 mJ/cm² 65 nm 78 nm Good 18 R-18 95° C. 28.0mJ/cm² 65 nm 82 nm Good 19 R-19 95° C. 24.0 mJ/cm² 70 nm 77 nm Good 20R-20 95° C. 29.0 mJ/cm² 65 nm 83 nm Good 21 R-21 95° C. 27.0 mJ/cm² 65nm 84 nm Good 22 R-22 95° C. 27.0 mJ/cm² 65 nm 83 nm Good 23 R-23 95° C.31.0 mJ/cm² 65 nm 83 nm Good 24 R-24 95° C. 27.0 mJ/cm² 65 nm 81 nm Good25 R-25 95° C. 31.0 mJ/cm² 65 nm 81 nm Good 26 R-26 95° C. 30.0 mJ/cm²65 nm 84 nm Good

TABLE 11 Com- par- ative Exam- Optimum Maximum Mask ple Resist PEB temp.exposure resolution fidelity LER 1 R-27 95° C. 24.0 mJ/cm² 70 nm 72 nmFair 2 R-28 105° C.  26.0 mJ/cm² 65 nm 84 nm Poor 3 R-29 105° C.  26.0mJ/cm² 70 nm 80 nm Poor 4 R-30 95° C. 21.0 mJ/cm² 75 nm 65 nm Good 5R-31 95° C. 22.0 mJ/cm² 75 nm 59 nm Good 6 R-32 95° C. 20.0 mJ/cm² 75 nm57 nm Good 7 R-33 95° C. 22.0 mJ/cm² 75 nm 67 nm Good 8 R-34 95° C. 20.0mJ/cm² 75 nm 58 nm Good 9 R-35 95° C. 20.0 mJ/cm² 75 nm 59 nm Good

It is seen from the results of Table 10 that the resist compositions(Examples 1 to 26) within the scope of the invention exhibit excellentresolution performance and minimized LER. In contrast, Table 11 revealsthat Comparative Examples 1 to 3, which use prior art resins, haveeither one of the drawbacks of inferior resolution and LER minimizationfailure. In Comparative Examples 4 to 9 wherein the inventive resins areused in combination with customary acid generators, it is difficult totake advantage of the inventive resins, and in particular, theirresolution performance is not improved over the prior art compositions.

Measurement of Leach-Out from Resist Film

Examples 27 to 29 & Comparative Examples 10 to 12

To 100 parts by weight of the resist compositions (R-01, R-05, R-07)prepared above was added 0.2 part by weight of a surfactant(Surfactant-1, shown below) which was insoluble in water, but soluble inalkaline developer. The resulting resist compositions (R-01′, R-05′,R-07′) and comparative compositions (R-30, R-31, R-32) were spin coatedon silicon substrates, then baked at 120° C. for 60 seconds to givephotoresist films having a thickness of 120 nm. Using an ArF scannerS305B (Nikon Corp.), the entire surface of the photoresist film wasirradiated through an open frame at an energy dose of 50 mJ/cm².

-   Surfactant-1: a copolymer of    3,3,3-trifluoro-2-hydroxy-1,1-dimethyl-2-trifluoromethylpropyl    methacrylate and 2,2,3,3,4,4,5,5-octafluoropentyl methacrylate in a    molar ratio of 20:80, with Mw=8,000

Then a true circle ring of Teflon® having an inner diameter of 10 cm wasplaced on the resist film, and 10 mL of deionized water was carefullyinjected inside the ring. The resist film was kept in contact with waterat room temperature for 60 seconds. Thereafter, the water was recovered,and a concentration of PAG anion in the water was quantitativelymeasured by an LC-MS analyzer (Agilent). The anion concentrationmeasured indicates an amount of anions leached out for 60 seconds. Theresults are shown in Table 12.

TABLE 12 Resist Anion leach-out composition (ppb) Example 27 R-01′ ≦5Example 28 R-05′ ≦5 Example 29 R-07′ ≦5 Comparative Example 10 R-30 30Comparative Example 11 R-31 35 Comparative Example 12 R-32 30

As is evident from Table 12, the resist compositions of the inventionare effective for preventing the generated acid from being leached outin water when processed by immersion lithography using water. They areexpected to experience a minimized change of pattern profile byimmersion lithography and cause little damage to the exposure tool.

It has been demonstrated that a resist composition which uses a polymercomprising specific recurring units as a base resin in combination witha unique acid generator capable of generating an acid having controlleddiffusibility is improved in resolution performance and minimized inLER, as compared with resist compositions of the prior art design.

Japanese Patent Application No. 2008-008890 is incorporated herein byreference.

Although some preferred embodiments have been described, manymodifications and variations may be made thereto in light of the aboveteachings. It is therefore to be understood that the invention may bepracticed otherwise than as specifically described without departingfrom the scope of the appended claims.

1. A positive resist composition comprising (A) a resin component whichbecomes soluble in an alkaline developer under the action of an acid and(B) a compound capable of generating an acid in response to actiniclight or radiation, wherein said resin component (A) is a polymercomprising recurring units (a), (b), and (c) represented by the generalformula (1):

wherein R¹ is each independently hydrogen or methyl, R² is an acidlabile group, X is O or CH₂, R³ is CO₂R⁴ when X is CH₂, R³ is hydrogenor CO₂R⁴ when X is O, R⁴ is a straight, branched or cyclic, monovalenthydrocarbon group of 1 to 20 carbon atoms which may contain aheteroatom, and m is 1 or 2, and said compound (B) is a sulfonium saltcompound having the general formula (2):

wherein R⁵, R⁶ and R⁷ are each independently hydrogen or a straight,branched or cyclic, monovalent hydrocarbon group of 1 to 20 carbon atomswhich may contain a heteroatom, and R⁸ is a straight, branched orcyclic, monovalent hydrocarbon group of 4 to 30 carbon atoms which maycontain a heteroatom.
 2. The composition of claim 1 wherein the polymeras resin component (A) further comprises recurring units (d) of thefollowing formula:

wherein R¹ is each independently hydrogen or methyl, and n is 1 or
 2. 3.The composition of claim 1 wherein the acid labile group represented byR² in said resin component (A) is one or multiple groups selected fromthe following formulae (a-1) to (a-8):

wherein the broken line denotes a valence bond, R⁹, R¹⁰, R¹¹, and R¹²are each independently a straight or branched alkyl of 1 to 4 carbonatoms, R¹³ is a straight or branched alkyl of 1 to 4 carbon atoms,cyclopentyl or cyclohexyl, “o” is 1 or 2, and p is 1 or
 2. 4. Thecomposition of claim 1, further comprising a tertiary amine as an aciddiffusion regulator.
 5. The composition of claim 1, further comprising asurfactant which is insoluble in water and soluble in the alkalinedeveloper.
 6. A process for forming a pattern, comprising the steps ofapplying the positive resist composition of claim 1 onto a substrate toform a resist coating, heat treating, exposing the resist coating tohigh-energy radiation through a photomask, optionally heat treating, anddeveloping the exposed coating with a developer.
 7. A process forforming a pattern, comprising the steps of applying the positive resistcomposition of claim 1 onto a substrate to form a resist coating, heattreating, applying on the resist coating a protective coating which isinsoluble in water and soluble in an alkaline developer, exposing theresist coating to high-energy radiation through a photomask, with waterinterposed between the substrate and a projection lens, optionally heattreating, and developing the exposed coating with a developer.
 8. Aprocess for forming a pattern, comprising the steps of applying thepositive resist composition of claim 1 onto a substrate to form a resistcoating, heat treating, imagewise writing on the resist coating with anelectron beam, optionally heat treating, and developing the coating witha developer.
 9. A process for forming a pattern, comprising the steps ofapplying the positive resist composition of claim 1 onto a substrate toform a resist coating, heat treating, exposing the resist coating tohigh-energy radiation through a photomask, heat treating, and developingthe coating with a developer, said process further comprising the stepof applying a protective coating on the resist coating, the exposingstep being effected by the immersion lithography wherein a liquid havinga refractive index of at least 1.0 intervenes between the protectivecoating and a projection lens.